I have had a problem recently whereby my Mavic 2 Pro refuses a command to descend.  I am using a Smart Controller.  When I give the command to descend it either descends very slowly (0.1m/s) or hovers and refuses the down stick command.  This is also the same if the drone is moving horizontally and a down stick command is applied at the same time. RTH does not make it land. I have to wait for the battery low warning and then the drone will land.   Anyone have a suggestion for this?  I recently swapped my drone using the care refresh but having the same issue which suggests it could be a controller issue?  The bottom sensors are clean so I dont believe it's an issue where it thinks the ground is below. Any help appreciated.

I have noticed this phenomenon myself a few times when light conditions were low or the landing surface had a marginal texture. After moving the aircraft slightly from the current landing location to a new one I could always execute a normal landing.

Hello there Ferg1174. I am sorry for the trouble this has caused. May we please know if you are receiving any error messages on the DJI Go 4 application when this is happening? Just a reminder that the DJI drone's vision system may not work properly when landing due to the lighting condition of the environment. Kindly please keep us posted for further assistance. Thank you.

DJI Stephen Posted at 11-1 22:39
Hello there Ferg1174. I am sorry for the trouble this has caused. May we please know if you are receiving any error messages on the DJI Go 4 application when this is happening? Just a reminder that the DJI drone's vision system may not work properly when landing due to the lighting condition of the environment. Kindly please keep us posted for further assistance. Thank you.

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No error messages have ever been observed and I have moved the drone over different terrain in order to remove any issue from the environment.  I should state that the drone is usually at a height of over 100 metres when this happens

MeAtHome Posted at 11-1 22:28
I have noticed this phenomenon myself a few times when light conditions were low or the landing surface had a marginal texture. After moving the aircraft slightly from the current landing location to a new one I could always execute a normal landing.

Thanks for the response.  This is occurring at 100 plus metres of altitude so I don't think that the surface is the issue here.  I have tried to move the drone to a different location to see if that changed things however it doesn't improve the situation.  I have to instead wait for the low battery warning to trigger a landing

Hi,

Best to get help/advice is to upload your flightlog(s) for his issue.

use this > https://www.phantomhelp.com/LogViewer/Upload/

post the uploaded link on here

cheers
JJB

Ferg1174 Posted at 11-1 23:17
No error messages have ever been observed and I have moved the drone over different terrain in order to remove any issue from the environment.  I should state that the drone is usually at a height of over 100 metres when this happens

Hi Ferg1174, we noticed that you mentioned that you've swapped the drone via DJI Care Refresh. May I ask if this drone is the replacement one? Could you please provide us with the case number(CAS) for a check? As for the descend issue, could you please provide us with a video and export the aircraft and controller log for our further analysis?

I had this once when the bottom sensors were blocked.

DJI Mindy Posted at 11-2 00:57
Hi Ferg1174, we noticed that you mentioned that you've swapped the drone via DJI Care Refresh. May I ask if this drone is the replacement one? Could you please provide us with the case number(CAS) for a check? As for the descend issue, could you please provide us with a video and export the aircraft and controller log for our further analysis?

Hi, yes this is the replacement drone that now has the same issue.  The CAS number was CAS-
7577703-Y9K8H9

Flight log here:
Flight log

JJB* Posted at 11-2 00:15
Hi,

Best to get help/advice is to upload your flightlog(s) for his issue.

Flight log here: https://www.phantomhelp.com/LogViewer/9WV9WZEFUH0JUPZ6GENY

Ferg1174 Posted at 11-2 01:30
Hi, yes this is the replacement drone that now has the same issue.  The CAS number was CAS-
7577703-Y9K8H9

Flight log here Mindy https://www.phantomhelp.com/LogViewer/9WV9WZEFUH0JUPZ6GENY

DJI Mindy Posted at 11-2 00:57
Hi Ferg1174, we noticed that you mentioned that you've swapped the drone via DJI Care Refresh. May I ask if this drone is the replacement one? Could you please provide us with the case number(CAS) for a check? As for the descend issue, could you please provide us with a video and export the aircraft and controller log for our further analysis?

https://www.phantomhelp.com/LogViewer/9WV9WZEFUH0JUPZ6GENY

Ferg1174 Posted at 11-2 01:32
Flight log here: https://www.phantomhelp.com/LogViewer/9WV9WZEFUH0JUPZ6GENY

Hi,

Easy log....

Flying high...mayby too high, at 5m28.5 sec in flight at 384 meter baro height the bottom height sensor is 'measuring' height.
See the chart. (green bold line = VPS height line)

First 8 meters false reading, but after that measuring false height of 1 to 0.5 meter.
This will reduce vertical speed down as drone thinks its close to the ground.
At 0.5 meter with 100% stick down it will enter landing mode.

Guess some moist on the sensor....

cheers
JJB

Ferg1174 Posted at 11-2 01:38
https://www.phantomhelp.com/LogViewer/9WV9WZEFUH0JUPZ6GENY

Could you please provide us with a screen recording and follow the steps below to export the aircraft and app logs for our further analysis? Below are the methods for exporting Aircraft and app log, you may upload the files to Dropbox or Google Drive, then share the link with us.
Aircraft log:
(1) Download DJI Assistant 2 from the official website. Download link：https://www.dji.com/downloads/products/mavic-2
(2) Launch DJI Assistant 2. Within 20 seconds after the aircraft is powered on, connect it to DJI Assistant 2.
(3) After DJI Assistant 2 recognizes the aircraft, choose "Log Export", and then click "Save to local".
(4) The final exported data are ".dat" files.
Smart Controller log:
1. Power on the remote controller.
2. Connect the remote controller to a PC.
3. Select “Transfer files” in the option appeared in the remote controller.
4. Open the hard disk root directory in the PC, and find “RM500” or the “Smart Controller” drive and open it.
5. Find the required log file folder based on the app’s storage path, and send the entire file folder. DJI GO 4: Smart Controller\ Internal shared storage \DJI\dji.go.v4\LOG.

Ferg1174 Posted at 11-2 01:32
Flight log here: https://www.phantomhelp.com/LogViewer/9WV9WZEFUH0JUPZ6GENY

Your flight data shows the VPS sensor giving false data that makes the drone think that the drone is just 2 ft above the ground.
Landing protection then slows the descent so that you don't have a hard landing.

Just a point, the Go4 app on a phone shows the VPS height on the screen.Below 1.2m the numbers are displayed in red.
The std controller, in the current test flight an RC1A, also shows the VPS height on its screeen as "clearance".
Either of those would allow this to be checked "live" without resorting to logs.

Does the smart controller display the VPS height on its screen?

JJB* Posted at 11-2 01:55
Hi,

Easy log....

Thanks for the explanation JJB. I didn't understand the VPS issue but do now.  I doubt that this is a moisture issue however as I have had the same thing occur on days of 35 degrees C and 20% humidity.  Given that it has happened with two separate drones using the same controller I am still thinking that there is something going on with the controller.  I swapped out the old drone with a replacement drone on the care refresh but it hasn't solved my issue.  Last time I reported this DJI told me to return the drone not the controller.  Appreciate your help

Does the smart controller display the VPS height on its screen?

Sean-bumble-bee Posted at 11-2 10:56
Just a point, the Go4 app on a phone shows the VPS height on the screen.Below 1.2m the numbers are displayed in red.
The std controller, in the current test flight an RC1A, also shows the VPS height on its screeen as "clearance".
Either of those would allow this to be checked "live" without resorting to logs.

Yes it does display on the smart controller.  If it thinks it is close to the ground why doesn't a down stick execute a landing?  Maybe a conflict with the altitude readout?

Ferg1174 Posted at 11-2 13:04
Thanks for the explanation JJB. I didn't understand the VPS issue but do now.  I doubt that this is a moisture issue however as I have had the same thing occur on days of 35 degrees C and 20% humidity.  Given that it has happened with two separate drones using the same controller I am still thinking that there is something going on with the controller.  I swapped out the old drone with a replacement drone on the care refresh but it hasn't solved my issue.  Last time I reported this DJI told me to return the drone not the controller.  Appreciate your help

Given that it has happened with two separate drones using the same controller I am still thinking that there is something going on with the controller.
It has nothing to do with the controller.
The VPS sensors are on the bottom of your drone and they are providing false data.
Are the sensors dirty?
Do you have any accessory fitted that might block their downward view?

Labroides Posted at 11-2 14:07
Given that it has happened with two separate drones using the same controller I am still thinking that there is something going on with the controller.
It has nothing to do with the controller.
The VPS sensors are on the bottom of your drone and they are providing false data.

I keep the drone meticulously clean. There are no accessories fitted

Ferg1174 Posted at 11-2 16:35
I keep the drone meticulously clean. There are no accessories fitted

Then the obvious thing to do would be to recalibrate the VPS sensors.

Ferg1174 Posted at 11-2 13:04
Thanks for the explanation JJB. I didn't understand the VPS issue but do now.  I doubt that this is a moisture issue however as I have had the same thing occur on days of 35 degrees C and 20% humidity.  Given that it has happened with two separate drones using the same controller I am still thinking that there is something going on with the controller.  I swapped out the old drone with a replacement drone on the care refresh but it hasn't solved my issue.  Last time I reported this DJI told me to return the drone not the controller.  Appreciate your help

Nothing to do with a controller, it is the bottom sensor reading false height.
Dirty, wet, moist, etc....

Does it also happens when flying at low altitude in flight the whole flight?

cheers
JJB

JJB* Posted at 11-3 00:44
Nothing to do with a controller, it is the bottom sensor reading false height.
Dirty, wet, moist, etc....

It has happened at lower altitude (40 metres or so). But it doesn't happen every flight.  Only every third or fourth flight perhaps