I had the same thought, but its not it. In this example, the slope angle for the agent is 45 degrees, the slope of the colliders in the stairs are at 35 degrees. Step height is at 0.8 units, which is way more than necessary.
I’ll try to reproduce the issue in a smaller scenario.
… While trying to get more data, I discovered that Navmesh Cut components cause even more connection issues.
Example video where I turn a navmesh cut on/off and how it affects pathfinding
When the cut is active, its as if too many connections get removed. Causing a “hard edge” in the navmesh.