Actually the simpler question would be to find out if there are any other Undead Slayers who experience the same problem. I know we don't have many, but it's a start.One other question I had, and I know this may sound like a silly one, but is it possible that you are inadvertently hitting the R key? I believe Quantum wears heavy armor (full/half plate) in combat, right? Hitting the R could potentially initiate a rest which would be canceled the heavy armor. It's been a long time since I've observed exactly what effect this would have on one's spells, so I'm not even 100% sure it will cancel buffs. I'm just throwing it out there as a possibility.
I never had this problem with Lex myself, when i was still a UDS, but granted i was not at the same level of UDS as Q is.Beside on some occasions when this happened to Q he was casting on me. The spells he casted on me did not dispel when his did. And the time it did dispel on him, he did not initiate a rest. Even if you initiate one and stops it the animation of the flying ZZZZ goes on.