UNREAL 4.21 - BUG Report - Nav Mesh Bounds not working only at persistant Level, why?

while working at main level, UE 4.21 crashed, after restart, persistant level´s Nav mesh doesn´t work, pressing P doesn´t work (no Green color), erasing and replacing with a new one nav mesh, doesn´t work either… i thought it was a problem in my level, so i created a new one, copied the not working nav mesh to that level and its working. But, why my original level doesn´t want the Nav Mesh to work? and copying same nav mesh to a new level makes it work? I already checked all my settings and compared both Word settings, no idea why this happens.

What can i do to fix Nav Mesh and main level? what else can cause this problem? Is this a Bug in UE 4.21?

I would love to know how to troubleshoot this better as well.

I didn´t found any solution…. i tried everything, but finally i had to rebuild everything in a new map……