Looks like the radius modifier only moves the path out away from bends without any other checks.
This works on meshes with plenty of room to move, but if the radius is wider than the gap between obstacles, the above can happen (Unlike the funnel modifier, it can push the path beyond triangle bounds).
In your example, you have a fairly high radius compared to the character (Radius of 1 vs 0.3), plus the navmesh itself looks like it already has the edge expanded to account for a similar amount.
The info here says good results would be from a mesh that’s been scanned initially without a radius at all:
Alternatively, If you’re using the recast navmesh, you could try lowering the cell size and/or max edge error to get smoother corners on the mesh itself at the cost of mesh complexity/generation time.