Well, I managed to fix it for about 2 seconds before I broke it again
Got all excited after the new capacitors finally showed up and went to put them in...
Accidentally left a piece of desoldering braid under the board and powered it up, something in this area let out a small puff of magic smoke. But I can't seem to find any burnt parts.
I'm pretty sure I blew something in the feedback curcuit, because it's now outputting 7V at enough current to spin a small motor. Voltage drops with load.
I'd hate to have put in all this work (and waiting!) and toss it now