You’re right, I wasn’t able to reproduce the issue in my sample project with an Invalidation Box element. As best as I can tell, when changing the visibility of the blocking SBorder element, the SInvalidationPanel widget has bNeedsPrepass set to false, whereas it’s true in the case of SRetainerWidget. I can’t quite get a handle on when or how exactly the two differ, but that does seem to lead to the invalidation panel recalculating its hit test grid, not leading to the issue.