So this seems to be random, right? Could be solely a Backburner issue?
I'm thinking so. No problems with the file since I restarted BB yesterday afternoon. Never had this happen before. I initially thought it was a memory issue, yet I didn't have any warnings and I wasn't even using half of my RAM. Chalk it up to a rare oddity I suppose.
I started looking into BB bugs, and it seems that to avoid some issues one should start Manager first, then Server (not vice versa). I never thought the order mattered, but many people seem to have an adapter error when starting the apps in the wrong sequence (happened to me also previously).
The best part of everything is that Autodesk either:
A - doesn't know about many bugs or can't reproduce them
B - they don't care.
I found a thread on their forums from 2013 about several BB issues, and then later in 2015 nothing had been addressed still. Can't say I'm not surprised.