Flying forward slowly (4m/s) and stopping the P4 will drop about 1/2 a meter in altitude.  It will then slowly creep back up to close to the stopping altitude.  My P3 did not do this.

Have you tried to defeat the Object Avoidance toggles in the DJI Go app?

Theresa Strange Posted at 2016-3-26 17:57
Have you tried to defeat the Object Avoidance toggles in the DJI Go app?

I have but not for this flight.  No obsticals were detected during this flight.  I was in a large open field and was setting way-points.  Each place I stopped the Phantom descended and climbed up again.

hummingbird.uav Posted at 2016-3-26 19:03
I have but not for this flight.  No obsticals were detected during this flight.  I was in a large  ...

You might want to verify. The OA is really invasive with flight controls.

TK-421 Posted at 2016-3-26 20:26
It has nothing to do with Object/Collision Avoidance (forward facing sensors), it has everything to ...

Also the RTH is pretty rough comparably with the P3P. That explains the symptom of fast descent/altitude difference.

It does this even for the P3 in P mode. But if you go to A mode it doesn't seem to do it as much even though it still has the sonar sensors. You can also turn off VPS in the settings I think.

What kind of surface were you flying over. There are limitations.

DJI-Ken Posted at 2016-3-26 22:31
What kind of surface were you flying over. There are limitations.

Ken here is an example of the stop and drop problem.   I believe the flight is higher than where the sonar works.

hummingbird.uav Posted at 2016-3-28 04:03
Ken here is an example of the stop and drop problem.   I believe the flight is higher than where t ...

It does look like you are above 10m, Can you try it lower about 20ft, then try it higher about 50-75ft to see if it still does it.

I experienced this issue twice now, both times were just a tad bit over 10m. Once was over a small pond and once in a parking lot. I have flown roughly 10 full flights so far and it has only happened twice that I realized but it can still be scary, especially when you're over water.

medicdanderson Posted at 2016-3-27 19:13
I experienced this issue twice now, both times were just a tad bit over 10m. Once was over a small p ...

I experience this over the following terrain:
dirt fields
grass
concrete
pavement

I experience this 100% of the time at any altitude. I've seen as much as a 9 foot drop in altitude then slowly climbing back to the original altitude. A lot of us have reported the same issue since we took the P4 out of the box.

I've had similar experiences where the Phantom 4 drops after stopping – perhaps 2-6 feet. Sometimes it doesn't do it, so I haven't quite figured out what's causing it.

I noticed this morning that after a few "drops", the Phantom thought it was higher off the ground than it really was. I took it down to one foot off the ground and it was reporting 9.8 feet of altitude in the DJI Go app. This is all on a flat field near the take off point.

I haven't had any close calls yet so it hans't been a huge concern, but I'm hopeful this is something that can be fixed in a future firmware update.

gamette Posted at 2016-3-29 00:40
I've had similar experiences where the Phantom 4 drops after stopping – perhaps 2-6 feet. Sometime ...

"I noticed this morning that after a few "drops", the Phantom thought it was higher off the ground than it really was."

I've seen the same thing.  You can visibly see the drop in altitude but the app still reports the same height.

Took it out a few times this morning with no drops. Like I said earlier, it has only happened to me a few times but when it does, it's scary. Something that definitely needs attention.

stshields91 Posted at 2016-3-28 11:08
"I noticed this morning that after a few "drops", the Phantom thought it was higher off the ground ...

Did another flight this afternoon and realized where this could become more of a problem.

I took my Phantom up to about 150 feet and flew around in Sport mode – about 1500 feet to the north and south.. I came back after about 9 minutes of flight and came really close to the ground – probably about 18 inches. The GO app was reporting the Phantom was 18 feet in the air.

I was wondering how that might affect failsafe RTH. Would the Phantom think it was higher than it really was when returning home? Not sure. In my case, it was wasn't a problem as the highest obstacles where I was flying were probably 50 feet.