I’ll bow to your knowledge on that one 
Which makes it even more curious. Its like I’ve missed something in the component itself… I might try taking it to a different build and see if I get the same result with that component. I didn’t think I’d need to do anything specific to register properties though. Whats weird is that you can cut and paste the values in the actual properties ok, so the property is there and has some area being drawn for it, it just doesn’t show the expand arrow or the checkboxes themselves.