First look is only a scan, because so many flights are affected. But there is a pattern.
Flight 7, dated in July of 2018, was a normal flight, and is the only actual flight prior to the trouble showing up. Flight 8 Dated February of 2019, was a crash. It recorded a motor failure at exactly the same time as the crash, so not clear which caused which. Need your memory of what happened on that date. That at least appears to be when the trouble started.
Big picture of the issue: You are having random single motor failures. Different motors. Often resulting in crash, but a couple times landed without crash.
There is some possible correlation between motor failures and swapping between angle mode and smart mode. That may not play out, need to study it more. But there is some sharp voltage drop associated with each flight mode change that is curious.
Altitude is not registering well, making it a little hard to judge exactly when lift off occurred.
Here are the flight numbers, followed by which motor failed on that flight. Interesting to see, but don't yet have even a speculation of why it is happening (other than the general "maybe the flight 8 crash shook something loose").
7 normal flight (2018/07/28)
8 motor 1 (concurrent crash) (2019/02/12) ( Do the dates for flights 7 and 8 look correct?)
9 Motor 3 (~6 seconds prior to crash)
13 motor 5 (off, restarted, no crash) (A motor restarting is new to me.)
17 motor 2 (off, restarted, no crash)
22 motor 3 (~7 seconds prior to crash)
23 motor 3 (no crash)
24 motor 3 (no crash)
26 motor 3 (concurrent crash)
27 motor 2 (restarted), Motor 4 (restarted), Motor 5 (~5 sec prior to crash)
29 motor 4 (concurrent crash)(also RTH activated at same time)
30 motor 6 (concurrent crash)
31 motor 6 (~3 sec prior to crash)
33 motors 4, 5 (Multiple motor failures, Drone on/off/on, No actual flight?)
37 motor 5 (~13 Seconds prior to crash)
This is just to let you know the quick look. I will have more time in the morning to look at this.
@Steve Carr is also looking, and is a much more advanced reviewer than I.
It is clear there are many random motor failure errors. What is NOT clear is if the motors are actually failing (and restarting), or if it is false errors.