Any potential reasons why I can't place a structure even though it's hologram is green?

Right now I’m working on a new Window Wall and Window, the blueprints of which are children of Window_Wall_Stone and Window_Stone_BP, respectively. Everything was working fine for a while - I was able to both place my new window inside of the hole in my new window wall and open/close it - But then I realized that the window wall was scaled to 0.95 height, creating a gap between wall and ceiling. I fixed this as well as a couple other weird scalings I noticed so that everything matched up with my regular walls, but then afterward I’m no longer able to place my window inside the window wall. The preview hologram still snaps and turns green, and I hear the little dull “dink” sound effect like it’s being placed, but the placement doesn’t actually happen. I think I’ve run into this a few times in the base game as well. But now I can’t fix it, I can’t figure out what I screwed up. So I need to know, what might be causing this? What does the game check for before doing the final placement? I already redid the collision mesh for both pieces just in case that was the issue - I manually redid the window wall collision because the auto convex collision was making a triangular shape in the window hole - But that didn’t fix it. I also tried scaling the window piece tiny so that there was an absolute guarantee of no overlap. I don’t understand perfectly how snap points interact between structure pieces, so maybe there’s configuration I have to do on both pieces to match up or something? Guidance appreciated, thanks!