I continue to be impressed by how on-the-ball you are! Last time I encountered this bug I assumed I'd just fatfingered alt-f4 or something, since you make pretty active use of all the modifier keys in keyboard mode.
I do have a weird setup in that I just upgraded my GPU and RAM but have an old processor chipset & motherboard - I recently found out I can't run After Effects, for example, and IDEs are chugging more now that I've started doing C++ dev. Timing sounds like a likely contributor as a result.
Anyway, glad I could help, even indirectly.