Hello,

I had a flight session today. I flew 2 batteries in a row without any issues, altough range was quite less than usually in very same conditions (same place, same firmwares, same frequency 5.8GHz as its the only one easily available here...)

During the 3rd fllight (3rd/4 batteries), I was taking some pictures (10 s intervall). At some point, I got a signal lost warning on the App. RC was still controling the AC and it was in visual range so I flew it back.
Even when the AC was very close to me such as a few meters, I never get back the video stream and connexion within app, RC was still OK.
It was in photo mode when signal was lost in case in matters.

I landed, loaded my last battery immediately and flew it without issues (i restarted DJI GO 4)

AC : 1.00.500
RC : 1.00.300
DJI GO 4 : 4.1.4 android (phone version)

Another small event :
During the flight session, I also has a gimbal motor overload warning at the very beginning; before takinf off. It wasthe first time I had this message. I took Spark in my hand, gimbal moved a little. I moved the pitch wheel one way ond another and message disappeared. I did not get it again after that.

If the drone lost transmission signal, that might because the drone entered to a place with magnetic interference and led a bad connection to the app or RC during that time, you can try to re-launch the app to see will the transmission recover. Please check is there many concretes around the flight place. You can also try to fly the aircraft in an open area. Besides, if the app pops up gimbal motor overload and disappears, that might be a false warning or the gimbal tilts to a certain place. Please have your drone stand normal and avoid reversing the drone expect IMU calibrating.

DJI Thor Posted at 2017-8-7 01:15
If the drone lost transmission signal, that might because the drone entered to a place with magnetic interference and led a bad connection to the app or RC during that time, you can try to re-launch the app to see will the transmission recover. Please check is there many concretes around the flight place. You can also try to fly the aircraft in an open area. Besides, if the app pops up gimbal motor overload and disappears, that might be a false warning or the gimbal tilts to a certain place. Please have your drone stand normal and avoid reversing the drone expect IMU calibrating.

It was the same place where I usually train, in the fields in the middle of nowhere. No concrete slab or walls closer than 250-300m away.
After I changed the battery and restarted the App, everything was ok again and it took only 30s to do that.

I therefore really believe that it was not real interferences, but rather a bug of app not able to reconnect to RC (altough .300 fw did adressed similar issues if I understand realease notes)

I can provide black box data if you think it helps to improve (I don't have Spark with me right now, can only do that next wednsday)

As for gimbal, I gace feedback because I saw other people claim issues since fw update. As for me, it must be a false warning.

Matioupi Posted at 2017-8-7 04:18
It was the same place where I usually train, in the fields in the middle of nowhere. No concrete slab or walls closer than 250-300m away.
After I changed the battery and restarted the App, everything was ok again and it took only 30s to do that.

Okay, please refer to the video below to export all the data, then upload them to the Dropbox. We'll transfer it to our engineers for analysis.

few things to try:

use OTG on tablet/phone with usb cable to the RC and turn off wifi/bluetooth on tablet/phone.

once you turn on the spark and everything so it is synced up at new locations, press and hold the button on the battery in the spark ..it should beep once and flashing will change, let go.  then RC press and hold Pause + FN +C1 the RC should beep at you, let it beep at you for a couple seconds before letting it go.. at this stage the RC and the Spark are searching wifi signals and looking for best signal and each other, once they find each other the RC should stop beeping and it should resynced.. at this stage video on screen should be clear and very little to no lag at all.. if half second or more lag or fuzzy, redo relinking processed i just told you again hold the spark higher up while it relinks..