RESOLVED: Worsening disconnections from AC => Overheating RC

KeithLa · Jun 12, 2018

Although there are already many other threads reporting close range mid-flight disconnections with MP, MPP, and MA, I'm creating my own post about my own recent experiences.

I'm fearing a physical hardware defect in either RC or MPP, given what I've witnessed and am reading on these forums. I plan to do some test flights in WiFi mode, without RC, to see if it's isolated to RC/Ocusync.

Narrated video of yesterday's latest incident:
Problem? Repeated, increasing occurrences of MPP disconnects from both DJI Go 4 app and RC, at very close range and low altitudes within minutes of takeoff, in multiple locations. In yesterday's incident, MPP lost connection only ~100ft immediately overhead from takeoff point, then unable to reconnect only feet away from the RC after its auto land descent.

RC has been unresponsive each time, so I only watch auto RTH and attempts to land. In attached video, yesterday it was stuck hovering over the ground due to false obstacle detection, see video.

RC showed full signal strength at all times, antennae correctly aimed, no signal interference warnings in the app.

Some very brief reconnects, updating RC status to "Landing", creating multiple cached video clips on my phone, and a second distinct flight record in DJI Go, even though there was only one takeoff.

Yesterday, power cycling RC reconnected the app and AC, enabling Forced Landing (whew). But in prior incidents, neither restarting DJI Go 4 nor RC worked, MPP only reconnected after it landed and was itself power cycled.

No apparent consistency on flight time, distance, or altitude when these disconnections occur.

Was unit in a crash? No

What have you tried so far?: Prior to takeoff, restarted phone and set airplane mode. Used high quality USB-C cable to bottom RC port. Restarted DJI Go 4 app after disconnect, did not help.

What device are you using? Moto Z2 Force: Very fast device (current flagship), Android Oreo

What firmware are you running (aircraft, remote controller)? Latest as of 6/11/2018

What Go app version are you using? Whatever version preceded this morning's auto-update, currently 4.2.20 on my phone.

Any modification? No

Did you change anything or install any apps? No.

Mossiback · Jun 12, 2018

I am normally quick to jump on the "an update caused the problem" bandwagon, but you stated that the problem is "repeated, increasing" so now I am thinking that perhaps the RAM on your Moto is filling up. See if you can clean the cache and delete any un-needed files.

KeithLa · Jun 12, 2018

@Mossiback do you mean local flash storage, or RAM? Not much I can do about RAM usage, esp. since the phone had been rebooted and DJI Go 4 the only app launched prior to takeoff. This flagship phone also has plenty of RAM.

That said, my local device flash storage is getting full (60/64GB used), however DJI Go 4 caches video to my external SD storage (39 of 64GB used).

Mossiback · Jun 12, 2018

KeithLa said:
@Mossiback...my local device flash storage is getting full (60/64GB used)...

That could be your problem. I don't know how Go 4 works (does anybody?), but it is normal for programs to write temp files while operating. Even though it is set to cache files to your external SD card it may first write to local memory before sending it on.

I may be fishing here but this is how many programs operate. Try cleaning up some of your flash storage and see if things change.

ac0j · Jun 12, 2018

I would think the device would only cause app problems and not the disconnect from the rc. The only thing that comes to mind is heavy RF interference or a problem with the drone or remote.

KeithLa · Jun 12, 2018

@ac0j, that's my sense, too. And I'm not the only one reporting this recently, here's another alarming post to DJI's forum today, reporting identical symptoms starting recently: Mavic Pro DISCONNECT?!

Hopefully that it's started recently for both myself and that longtime MP owner is evidence of a fixable firmware bug, not HW defect.

I'll probably try downgrading the firmware revision next.

Mossiback · Jun 12, 2018

ac0j said:
I would think the device would only cause app problems and not the disconnect from the rc. The only thing that comes to mind is heavy RF interference or a problem with the drone or remote.

OK, I missed the part about disconnecting from the RC. That would lead me to consider a firmware problem with the RC, MPP, or both.

KeithLa · Jun 24, 2018

Happy to update here that after further troubleshooting of these close range aircraft disconnections, I ascertained my RC was faulty, seemingly overheating ten or so minutes into flights in warm outdoor temps (80-85F). My several observations that led to this:

- Immediately after random aircraft disconnects, Djigo4 reported RC firmware as 00.00.0000
- Power cycling RC would reconnect to AC and Djigo4, but only sporadically, just enough time to force land
- RC fan noise not present as usual, quieter or not running at all, and felt hotter to touch than normal.
- After power off and cool down, RC would connect to AC, and Djigo4 showed RC version 01.04.0300, but firmware refresh would fail. (Interestingly, it downgraded ok to 01.04.0200, but wouldn't go back up to 0300.)

After an hour online chat with DJI Support describing these conditions, they concluded RC must be faulty and should be returned for diagnosis and repair. Instead, I took advantage of Costco's 90-day satisfaction guarantee, returning the entire MPP/Goggles bundle for a brand new one, no questions asked.

I've had no RC aircraft disconnects with the new gear, and am now flying much greater distances without incident. Well, almost no incident: On one recent flight, my new DJI Goggles disconnected and Djigo4 reported 00.00.0000 for *their* firmware version, but the RC performed flawlessly. Not sure what happened with these goggles, hasn't happened since.

No idea what might have caused the RC to become faulty, but I'm taking care to only charge the new RC with the Mavic AC adapter, for starters.