floating unsimulated fragments in geometry collection?

UnrealEditor_S5FMsNojv8

I am trying to set up a breakable window. In the image above the two floating frame pieces are there intentionally as placeholder static fragments to hold the geometry collection in place, but the glass fragments in the centre are not. I have checked and the centre fragments have the exact same settings as the fragments around them that break as intended. I am not sure what the issue is.

I have also noticed that these fragments do not collide with anything at all. They do move with the rest of the mesh if it is falling, but once things start to break they stay put at their position in world space and do not collide with anything.

Anyone have any ideas?