It's actually been a while since I tried to play songs from my Nas, but I faced an issue.
Some songs or albums are not playable after added to the queue. Or, for others, the track length is not correct. Some though are playable.
I first thought it might have something with enabling FFmpeg, but it doesn't.
What I suspected next was the way rAudio interprets cue files. Didn't investigate too much but if I add a file/album with an external MPD remote (I use M.A.L.P which is awesome) it does add, and is playable even through rAudio web interface.
My version is 20210302