I haven't experienced it in BiaB, yet my instinct says 'buffer unload'.
Likely induced by driver/system combinations and hard to isolate. But that's just a guess.
Most likely my fault. wink

Buffer dump has been the issue the few times I *have* experienced this with RB. I've never seen it in BiaB though. Then again I spend much more time in RB than BiaB.
In RB I've seen it both at the end of songs and when I stop a song (before the end) and restart it right away. However, in these instances, I can usually track it back to an isolated FX plugin being used. The plugin gets stopped with it's buffer still holding data, and empties it suddenly. This may be another clue.

/Not isolated to a single plugin; seems to be a plugin/system combination event

Make your sound your own!
.. I do not work here, but the benefits are still awesome