This may seem odd, but have you tried a different mesh entirely with the same BP setup? If not, try with something like a cube - create a DM out of it and see if that acts differently. I’ve experienced weird things where the DM was the issue itself not breaking via BP but would otherwise. I cant remember exactly what the issue was with the mesh (maybe had holes or something), but at least that might get you a step further if it is the mesh itself.