Will give it a go, the ball doesn't eventually come out of the Swamp! Self test on start up doesn't give any reports either.

When does the lost ball come out of the kick out? Does the ball kick out normally when you drop into the swamp? Does the ball kick out normally when entering the kick out from the playfield? Does show time multiball work normally?
Just me but I would run these processes as well as the quickmulti ball manually with the game sound turned down. You should be able to see and hear the assembly through the coin door to see if the transfer solenoid fires etc. (maybe a small mirror will help) Finding where the ball is stuck may help you diagnose the problem. You would need to tape the coin door switch closed of course.