combobox inconsistently active/inactive

I’ve run into an annoyance that I can’t seem to resolve. I have a basic dropdown combobox, and I add it to the viewport at the start of the level. it goes invisible initially. Later when the user activates it, it appears at the mouse and disables when they click again, using a flip flop. This all works fine but sometimes the dropdown works, and sometimes it does not (it cannot be clicked, as if it inactive. I have active bound to a boolean var that I set from another blueprint.

Am I missing something? I get no errors, and it isn’t consistent. If I start the game and activate the dropdown in the same pattern, it may or may not work.j