Hey, thanks amigo — that helped me realize this problem is probably because of the Platform behaviour not being able to climb inclines. (attached photo shows the character stalled because of the incline)
I did a more comprehensive overlap test, and no matter how many overlaps it checks, the character won't move forward until the cog is below a certain angle.
Has anyone had any experience with the Orbit behaviour? I thought that could be useful here, but I've not had any luck with it.