Maybe this is something you already met, I am struggling to debug precisely. I have a bridge, which has very small holes between wooden parts and it is part of the navmesh recast graph with “mesh collider”. Normally nobody falls through, as their colliders are a lot bigger than those holes.
However, rarely when unit is changing AnimatorController (my guess, because it only happened so far during attack when override controller is applied/removed for specific weapons) while standing on a bridge - it might fall through. (Maybe its unrelated though)
As for the settings, I dont use Unity Gravity. But on AIPath i have custom gravity enabled and setting “constrain inside graph”. Maybe its the raycast of the script hits the hole?
What possible solutions I could consider besides making an invisible mesh inside the bridge?