Seller doesn't always come. Reboot seems to solve. Beta 12
In multiple Japanese villages, (have not encountered other cultures yet, (EDIT: can confirm, it happens in all cultures.) the seller may or may not announce she is coming, often does not, and then doesn't come at all. Sometimes, if I went to find her, if she was stuck on a block, i could free her, but more often it required a reboot of my server to fix her behavior. Problem would generally crop back up again soon after.