I am simulating an environment containing sphere-like agents and ramps. An important feature of the environment is that agents can slide up ramps (see screenshot below; agent in red and ramp in blue). In addition, I would like to measure distances between agents and specific geoms using inactive contacts. My understanding is that if I set the margin/gap parameter in the agent xml to an equal positive value, inactive contacts are enabled but the physics should be unchanged. However, it seems that setting agent's margin/gap parameter is changing the actual contact forces. When agents approach the oblique side of the ramp, the contact force is horizontal to the ground (as if the ramp were a box) and agents cannot slide up the ramp anymore. If margin/gap is zero, this problem does not occur (the contact force is vertical to the oblique surface). Is this a bug in Mujoco and/or is there a workaround?