Collision issue with my BSPs after lighting testing, bug or noob?

Trying to learn a few things about blocking out with BSPs and simple lighting. Beginner level.

After not getting the lighting results I wanted, I tried setting my BSP brushes to “movable” rather than “static” (this might have been nonsensical, but hey :slight_smile:
Problem was, after saving and restarting the editor, all BSPs became invisible (static meshes and terrain were fine though). After painstakingly setting all BSPs back to “static” again, they could be seen, but had lost their surface material. After painstakingly reassigning their materials, things finally looked like it did before, but playing in the viewport now revealed that all subtractive brushes now had collisions, and I can’t walk through any doorways or openings.

Here, I’m stuck and can’t seem to find an answer. Anyone feeling like being my hero and telling me where I did wrong and what I can do to fix it?