Converting brush to static mesh issue. Disappearing brush polygons

Hello.
I am using UE 4.21 for my project.
During production I noticed that at a certain amount of brushes, some of them are cutted off: some polygons just disappearing. Build All button didn’t help.
I tried to convert brushes to Static Meshes. When I press a button and enter a proper name, my brush teleport at 0;0;0 and no mesh was created.
Please help with those 2 issues.

I figured out how to create static mesh. I move brush to Persistent level, then convert it ti static mesh, then return back ti its level. Well…it works. But questions are still up

Thanks for sharing how you have solved this issue. It worked for me too!

This helped, thnx!