Follow the 81D circuit. If the direction pilot relays (81D's) don't pick on a reversal, car calls won't latch + it won't answer and reset a down call. I'm assuming it's a 7 stop? What happens if you drop 81U's manually? Will 81D's pick? SIngle car? Sounds like an interesting problem, never seen this one in particular. I would also look at the SO relays, it's happening at two floors though...