EDIT: I guess I should've tried reloading the save to see if the bug actually reproduces. The sheriff seems to politely walk away from the stockpile right after you load that save... and after running around for a bit seems to come back to begin his stockpile dance again. I guess this still might be able to reproduce the problem.

This demonstrates one of the various equipment bugs in the .31 line of Dwarf Fortress.
This specific save has at least the sheriff(belonging to the military) trying to pick up some equipment from a stockpile, walking away and trying to immediately repeat the same trick, resulting in him getting stuck in some sort of a loop.

On a lesser note, none of the miners (who belong to their own dedicated squad) in this save don't seem to realize they have a pick equipped, at least judging by the lack of a check mark next to the pick on the equipment menu.

The DF version this was saved on is 0.31.06, the dropdown menu just didn't have the option for it yet.