I stayed overnight at Swinesbury Academy and the shop owner slept at night, but in the morning when he woke, he started running into the right side of the building as if running to get an item, or to run home. At dusk however, he returns to normal behavior. This happens over and over every night I stay inside.
This has also happened at other pig owned establishments.
Start a new game, no mods, default everything. Go into Swinesbury Academy and stay overnight.