What made me question a tree strike was that there is no prop damage at all. I’ve flown many craft, from 35% scale planes to 25% helis. Typically if a blade or prop hits a tree, you know it.
I totally understand your idea but what you have to mind is the rotary mass and the stiffness. The moving parts on the H520 are fairly lightweight and the Props are very flexible. I never had an OEM prop fail on my Typhoon H. Not even when it tipped when I landed on a rough and hard ground during windy conditions.
When flying my FPV racing drones I noticed that even a slight contact has severe effects on the flying characteristics. Especially when you are flying slow a contact with thin leaves and branches will already pull you towards the tree since the propellers on that side are slowed down. When you are going like 80mph however, the same leaves and branches will hardly slow you down at all. Even though the props are spinning at more than 40.000rpm they will only brake on very rare occasions. Usually only the leading edge gets eaten away until you start to notice an increase in noise and vibration.
In summary I am not surprised that your propellers are not broken.
The other thing that made me question a tree strike is that just before the crash, the video started lagging badly and even had a black screen for a split second. I was not sure if there could have been a connection problem due to the density of the trees.
Since you were flying low in a distance of about 316m (just below 1000ft) without a direct line of sight, I guess that was related to a poor video signal. Unfortunately there is now useful RSSI reading in the log so I cannot give a clear statement. But what you can see is that the signal failed entirely just 4s after the motor 4 error was noticed.
What I also found interesting is that motor 4 was indeed the first motor to notice an issue but not the last. Within the very same second all six motors recorded the same error. That also supports my thesis that the drone collided with a tree since it indicated that none of the rotors was able to spin freely while the drone was still falling towards the ground. Also the fall took a lot longer than you would expect for a free fall. The drone started falling after around 3:05.775 of flight time and touched the ground at 3:08.580. Almost 3s is very long for a fall of only 12m (39ft). Therefore it is very likely that the fall was slowed down by something. The drone itself has most likely only contributed very little since it was spinnging around all axis and was even upside down for a moment.
In conclusion I am almost 100% sure that it was a controlled flight into one of those trees. All the data collected show perfect health of the aircraft itself but do show a lot of indications towards a collision.