I was flying the P4P out of sight behind trees this morning and began to lose the RC signal.  I tried to gain altitude and DJI Go crashed (iPad Pro) and displayed the iPad home screen.  I checked, and the DJI Go program was not running in background. I restarted the software, while also holding the left stick up, and the AC appeared in line of sight.   When DJI Go started again, it would not establish connection to the AC and displayed "disconnected" on the DJI Go screen.  Even with the RC within 100 m and in sight, it still would not connect  The compass on the screen was however still functioning, everything else, blank.  I felt under control, so I tried a RTH on the RC, and got no response from the AC.  I landed, restarted the iPad, RC and the AC and all worked fine again.  I have not updated to the newest firmware, so that cannot be to blame, however, I was taking a series of photos at the time in quick secession, with a 64GB card that is about 60 % full.  I am intimately familiar with both objective C and swift, and suspect that the DJI Go program was not to blame.  I suspect, that the RC or the AC software (language unknown) may have been running in a truncated manner since both control sticks functioned, but not RTH, or full feed to the iPad.  This leads me to believe it was the software on the RC that failed, and may have been directly related to the latency caused when writing both DNG and jpg files to the memory card.  I was fortunate to be close enough to the AC to fly home visually, but had I not been, I would have powered off the RC and hoped the AC would return on it's own.  I have made over 400 flights, and this failure scares me, especially since the RTH from the RC was not effective and AC did not respond.  

Does anyone have any thoughts about this incident?

Have you heard the ''Beep, Beep'' after you pressed the RTH button?

DJI Thor Posted at 2017-6-23 00:25
Have you heard the ''Beep, Beep'' after you pressed the RTH button?

There was a beep only when I pressed the RTH button.  No beeping to indicate the RTH function was active.  Also, the chevron for the AC was in the centre of the compass indicating the AC orientation only, not the direction the AC was from Home or from the RC.  There was no "H" in the centre of the compass.  Obviously the AC and DJI Go had lost the home point.  Fairly sure the AC did a reset.  The log files show too that the starting point, after I had returned and reset everything (at the home location), was the last location the AC was at the point of failure, not the home point.  Weird or what?   I will have to do some testing before I can trust the AC again.  Had I been further away and been unable to see the AC at the point of failure, I am fairly sure I would have lost the AC.

JW5255 Posted at 2017-6-23 02:23
There was a beep only when I pressed the RTH button.  No beeping to indicate the RTH function was active.  Also, the chevron for the AC was in the centre of the compass indicating the AC orientation only, not the direction the AC was from Home or from the RC.  There was no "H" in the centre of the compass.  Obviously the AC and DJI Go had lost the home point.  Fairly sure the AC did a reset.  The log files show too that the starting point, after I had returned and reset everything (at the home location), was the last location the AC was at the point of failure, not the home point.  Weird or what?   I will have to do some testing before I can trust the AC again.  Had I been further away and been unable to see the AC at the point of failure, I am fairly sure I would have lost the AC.

Normally, you should press and hold the RTH button to start the RTH procedure, If the RTH is triggered successfully, the LED ring around the RTH button will blink white with beeps. You can export the data of this flight, then send an email about this to support.us@dji.com, we can submit a data analysis to check it.

DJI Thor Posted at 2017-6-23 03:05
Normally, you should press and hold the RTH button to start the RTH procedure, If the RTH is triggered successfully, the LED ring around the RTH button will blink white with beeps. You can export the data of this flight, then send an email about this to support.us@dji.com, we can submit a data analysis to check it.

I did the RTH properly, but I should send the logs, after a review, it appeared to happened with my P4 as well, but I had not noticed it at the time.  Would appear that the GPS signal was lost.  Odd, it shows to have happened only yesterday.  No other time.  I might add that a cell phone was in use with 10 meters of me during the incidents.  I will send the logs ASAP.

JW5255 Posted at 2017-6-23 03:53
I did the RTH properly, but I should send the logs, after a review, it appeared to happened with my P4 as well, but I had not noticed it at the time.  Would appear that the GPS signal was lost.  Odd, it shows to have happened only yesterday.  No other time.  I might add that a cell phone was in use with 10 meters of me during the incidents.  I will send the logs ASAP.

OK, my colleague will help to raise a ticket to data analysis team for further detection, if you have other questions, please keep us posted.

JW5255 Posted at 2017-6-23 03:53
I did the RTH properly, but I should send the logs, after a review, it appeared to happened with my P4 as well, but I had not noticed it at the time.  Would appear that the GPS signal was lost.  Odd, it shows to have happened only yesterday.  No other time.  I might add that a cell phone was in use with 10 meters of me during the incidents.  I will send the logs ASAP.

If you're really stuck, then the best way to initiate RTH would have been to turn off RC. The aircraft will autonomously start an RTH after three second loss of control signal. In fact it may have started RTH itself, and by pressing the RTH button you may have disabled it again. The records should reveal all.

Aardvark Posted at 2017-6-23 04:37
If you're really stuck, then the best way to initiate RTH would have been to turn off RC. The aircraft will autonomously start an RTH after three second loss of control signal. In fact it may have started RTH itself, and by pressing the RTH button you may have disabled it again. The records should reveal all.

I was thinking the same thing, however, I am fairly sure the AC reset and Home coordinates were lost, so the RTH became ineffective.  But as I mentioned, it happened with the P4P, which I noticed, but my logs also indicated it had happened when I flying the P4, which I had not noticed.  During both flights, the same cell phone was in use a short distance away (10-15 m), so I am highly suspicious that the cell phone signal had interfered with the RC signal and caused an AC reset.  Maybe !??  This issue occured only on these two flights and all later flights were fine.  I will do some field testing though, to assure I get my confidence back.

DJI Mindy Posted at 2017-6-23 04:20
OK, my colleague will help to raise a ticket to data analysis team for further detection, if you have other questions, please keep us posted.

Will you be sending a ticket number?   If yes, will it be sent via the forum or email?

DJI Mindy Posted at 2017-6-23 04:20
OK, my colleague will help to raise a ticket to data analysis team for further detection, if you have other questions, please keep us posted.

I have the same problem here, even if dji go 4 app does not crash. It only connects again if I disconnect the cable and reconnect it again.

JW5255 Posted at 2017-6-23 05:00
Will you be sending a ticket number?   If yes, will it be sent via the forum or email?

I'm sorry that I'm unable to open the ticket for you, please contact our support by the phone or online chat: http://www.dji.com/support Thank you for your understanding.