I've also had this same problem - since I purchased the unit around spring last year. Just randomly stops playing (through Kodi and wrapper),using NAS and wifi. I thought it might be Google notifications that were interrupting so switched them all off - however it still happens. I'm on firmware 2.05.
It's really annoying especially when playing something for the kids (who at present can't operate the remote etc) and it suddenly blacks out half way through the movie.
I've had to revert to my WDTV Live at times just to be guaranteed it won't cut out, especially if watching with friends.