Question about pinjoint and glitchy rotation

Godot Version



I’m trying to achieve a custom player scene that is controlled by physics but also controls well on the ground. my current approach is just to put a wheel on the character which touches the ground, so that it can have friction and response to moving platforms, but spin freely whenever they choose to move. the wheel is pinned to the parent character by a pinjoint2d.
It sort of works, but for some reason the wheel rotation occasionally glitches for no apparent reason. Can anyone speak to it?

Just move the character left and right on the flat section at various speeds and I think it will be visible. It happens even if you comment out line 57 in (although it becomes more subtle)
I’m interested in it being smooth because I’m contemplating having the wheel position drive the frame of the running animation (not currently implemented in this project).

Also another non-physics question: why does the character start considerably farther right and down from where he is placed in the scene?