Just curious,

I have an 84 Guerciotti and put a 68x110 bb in it with a campy chorus crank, on the drive side the cup has unthreaded about a quarter of an inch and when I thread it back in, it threads our again. First, how is the possible when the drive is going forward and it has to back out of the threads in reverse. Is it possible that I have it put on where the drive side should be on the other side of the bike. Not sure how this happens and just need some friendly assistance.

Thanks
Mark