Hello,
  
  Even though I have just about the fastest Android phone available (at  least until the Samsung S8 comes out) the DJI 4 app consistently  crashes.  Every single flight the app crashes mid-flight, sometimes more  than once.  I decided to install Litchi and that app hasn't crashed  once in over 40 hours.
  
  While Litchi is much more stable, even with the AirData integration you  don't get the view showing your flight data in movie form like the DJI  app, e.g., no stick movements, 8x replay, wind warnings as part of the  replay, etc.  
  
  The issue is when the DJI4 app crashes it only retains the portion of the flight after the  app reconnects - so if you really had a 23 minute flight and the app  crashed at the 20 minute mark, the DJI app only shows a 3 minute  flight.  So right now, the app says I only have 4 1/2 hours of flight  time when it's about double that.   The app has crashed in all  firmware/app versions I've used (.400 and 4.0.4).  Finally, the app also  no longer captures any pictures thumbnails for each entry in the log  (it did initially).
  
  If the app doesn't actually store the full flight data when it crashes -  how on earth can DJI assist me if there was a warranty claim and they  needed to know what happened, if there was user error, etc.?  More  importantly, is the flight log data stored on the Mavic itself so that I  can retrieve it another way?  If so, would it have the same information  the app has (stick movements, 8x replay, etc.)?
  
  Environment
  Mavic Firmware: .600
  Device: OnePlus 3T - Android 7.1.1
  DJI App: 4.0.7

There's another log that's stored in your Mavic itself and that's the log DJI will preferentially want to look at, I suspect it has more info than the one saved to your phone, but I'm sure it has at least the same data set. It's accessible via the DJI Assistant app.

As for your phone, can you downgrade to Android 6? That seems to solve the problem for some users.

Have you checked to see if there are not more than one flight log for the same flight.
When I was using android and had app crashes, it would split the flight such that I had a partial log prior to the crash and a partial log after the crash.
The other thing to check is your cache setting. It might be that there is insufficient cache to store both pre and post app crash so the pre crash part is deleted.

Don't trust flight logs stored on the Mavic. I've sent it to DJI for a review and they told me they "couldn't analyze it for various reasons" and asked me the flight logs stored on my phone

Apologies for resurrecting a thread from last year, but I've just encountered this same problem: app crashed while my MP was 750m upwind and at 350m altitude - just after I started getting "high winds" warnings. In the five minutes or so that it took to get the app re-started, those winds had carried the drone 1.5km downwind (weather reports gusts of up to 40kmh), so now on the wrong side of the wind for the return journey with decreasing battery. In the end, I had to execute a forced landing and everything seems OK.

But when I went to review the flight log, there's only one entry for today - the 8 minutes spent battling the wind to get home, and none of the 20-ish minutes of the planned flight. Apart from the annoyance of not having a record of this flight to match up with the footage, the "total flight time" info in the side panel is obviously useless if it discards 80% of the data.

I'm using the current version of the app, so can I assume that there's been no effort to fix this, or is there some setting or recovery protocol hidden away in a menu somewhere?