Don't laugh, but I'm still on 5.1 on my original 2013 Moto X, because there hasn't been a phone released since then that can beat it.
I understand sticking with something that you like... though I must say I didn't like my wife's Moto X. I don't remember what version she had (weren't there two?) At any rate, I get it!
I sent in a debug if it helps.
The error is pretty darn generic but
seems to indicate that the VideoView can't play the files. Which doesn't make a ton of sense to me but COULD be accurate if that particular Android component wasn't finalized back then (this isn't indicating the phone can't play it, just that standard video display control).
I have an alpha version that swaps it out for the VLC player library... this can play MANY different video types that are independent of the system's codex. It hasn't been very well tested yet, though is working fine in my minor tests. If you want to try it out, send me your google account email address (pretty sure this is all I need to enroll you) via a PM.
Adam