Welp, can't explain the earlier behavior exactly, but on the way home from work today she was hard broke and stuck in the vent position. Didn't respond at all to any button push.
Took everything apart and the black plastic "cover" from the top of the motor is shattered to little pieces. I've no idea how long it's been like that.
If you've never seen this thing, it takes some study to realize that it's not just a dust cover, but an integral piece of the system that holds the gears and some other tiny bits in their proper places. So, naturally, some internal motor bits were allowed to move in ways they weren't supposed to.
My gears look fine. No sign of wear or deformation at all. It looks to me that if I could just replace that cover, I could put it all together again and it would work.
I figure there's a snowball's chance in a Texas July that this piece is actually available. I'll keep searching, but if anyone has any tips on where to look or what to call it, I'd appreciate it.
