I admit, that was a poorly constructed paragraph in a moment of blind frustration lol. Basically: Create brush, turn into func_wall, create trigger brush and link the two. compile. When I try to activate the func_wall brush in game, nothing happens on first attempt, but if I try to activate the func_wall a second time it works as expected. Now say I do the same again except tick the 'start off' key, then compile, when activated in game the func_wall triggers first time as expected. The issue is just when the brush doesn't have the 'Start off' key selected, when you try to trigger the brush in game, it takes two activation attempts, and i've no idea why..