I was hearing some .flac files, and I see some files just stop playing out of nothing, it always happens around 3 minutes.
So far, two .flac files (from very few audio files on HUB) just stop with no reason.
I’m using the last FW, to me is another bug. 
What other details are you kindly able to share with the WD Community as well? You make mention of some FLAC files, do you obtain the same response from your other FLAC files?
More details will allow more Users to better help you.
Regards,
I had this and found very small “Jumps” (similar to when the needle jumps on a vynal regord) and this is enough to make the player move to the next track.
I resolved this by re-ripping from the CD, what’s very annoying is that they will play perfectly on a PC using VLC!