2 identical Raspis: (1) one plays, the other won't (2) error log says can't display files

I bought 2 identical Raspies (3). Identical setup.

(1) Both played for a while, then one stopped. Can't get it up again, schedule does not work. Only solution: go to the venue, unplug, restart. They're both in the same wifi network and access the same server. 
(2) the working player shows a massive errorlog, see screenshot. i can't see whats wrong with the files. none is bigger than 10 mb. they are all .png. whats wrong?

R.