RVO Controller not walking stairs

I am using the RVOController for a creature to wander a layered grid graph. Everything is working great except for stairs. The pathfinding appears to be correct based on the drawn gizmos but the creatures does not walk up the stairs but falls through the ground.

I have created the RVOSimulator and RVO Navmesh:

This image shows the gizmo traversing the stairs but the creature is sinking through the stairs:

The seeker script is set to use ground:

The RVOController is set as follows (I circled the settings I am suspicious of but I am not sure how to use them):

Hi

Is it possible that the height of the character (0.3 in your screenshots) is lower than the size of the steps? In that case it would think it moved below the step.
Try to increase it so that it is approximately the correct height for that character.