Is there a way to change union collision failure?

[SkaleKill]

I was doing map for my game, but even with the precise colisions it does some weird and annoying things that idk how to change. by exemple :

without showing geometry;

showing geometry.
As you can see, the hole is partly filled with collisions, and idk how to change it… is there a way to “erase” this failing collision? Thanks for all!