Update: Turned out there was nothing wrong with the Jazz/Rock mini toggle switch. The problem turned out to be that the lead from bass pot which is soldered to the top terminal on the switch was so long that it was touching the terminal below... I simply had overlooked trimming away the extra wire after making the connection.
I'm so glad I didn't have to change out the switch and re-do the wiring in that very tiny, very cramped space!
I going to continue to play the amp for a few days before installing the Tube FX Loop... update to follow.
EDIT: Well crap... the switch is bad after all. At least the new switch is here. I'll get it installed tomorrow.