I didn't think it was, it just kept appearing the log. I wonder if continual failed attempts to extract thumbnails, may be having negative a effects.
Could you please try the following as test:
Remove the cache settings I suggested, as they didn't help.
Copy one of clips to usb, (I know we've tried this before...)
Isolate the vero4k from the network.
Playback video, with adjust frame enabled and then try again without.
Reconnect to network and upload logs.