I saw it a few times. A pig just can't get inside his house and at evening and night time.
In the first screenshot he was just stuck "running into the red house" (but his house is green). When i reloaded the game ("save and quit, then load again"), he absolutly easy went into his own green house. Hmm...
In the second screenshot, a pig simply couldn't get around the wall and continued to run to it's house until the morning.
Steps to Reproduce
Walk around the city at the evening and night time.
This issue has not been confirmed by a developer yet.