Log is somewhat inconclusive, which itself is an indicator. First, there was about a 2 second gap in the log data before it crashed. Then at the very end, the copter appears to be tumbling. The 5v power to the cube sharply drops, and the log abruptly ends. There is no change to auto mode in the log. And no other meaningful information I can see.
I think you had a power failure, or something along those lines. It doesn’t appears to be any specific motor failure, or anything you did wrong.
There is nothing unsafe about 1.3.1. That’s what every unmodified solo is flying and has been for years. Upgrading to 1.5.4 doesn’t functionally change anything related to the ESC issue, and both have the same protection in place. I do not see any motor loss in these logs.