Marius has been standing in front of the stand where Henry deals with town affairs, he doesn’t move from that spot and will not move to the garden to start improvments even after the option is selected
I’ve had that bug.
Wanting him to break out of his state, I sneaked up behind the church at night and shot an arrow that landed near his feet. He ran to the village outskirts and just stood still there instead. Later I shot another arrow, and he ran back to the village green.