You can snap anything to the grid, the question is how accurate will the angle be after. It might be slightly off, but better to be a little off & on the grid that perfect and off the grid.

yup, radiant has never been able to handle brushes at angles, so stupid, just use prefabs, so make the brush and detail in  prefab at a standard angle, then rotate the prefab in map

Not ...

Sometimes the compiler will try to merge concave surfaces together and generate unwanted collision. It looks like that's what you're seeing here. There are 2 ways you can go about fixing it:

1 - Make all surrounding geo non-colliding and manually clip it (brushes only, no patche...

A little late to reply, sorry.

Before this error popped up, did you recently modify a buyable? Could be a door, weapon, boards, etc.. My guess is you left some part of the ent structure behind without realizing.

Alpha gameplay video.

Windings errors typically have to do with terrain or curve patches. You should take a look at any recent changes you've made and look for any geo that may be overly complex or large.