Had the same bug pop up yesterday.
Wilderness farm map, so it seems like the bug isn't affected by map type.
As I entered the farm by the southern entrance, a cutscene triggered; Leah visits to give the farmer her "How I Feel About <your name>" sculpture.
After the cutscene ended, I was back at the southern farm entrance, but my farmer had reappeared too far to the right by half a tile and was stuck. All he could do was run on the spot, or turn around in place, up, down, left and right.
I had Leah's sculpture in my inventory, so I tried placing it. As you can see in the attached screenshot, it's aligned correctly, but I couldn't interact with it in any way.
My lil farmer was stuck there until he passed out at 2 am.
Edit: Oh yeah, and I even tried the "wave your sword continually to go out of bounds" technique, but still couldn't move.