Left click detection in spectator mode

I made this menu that uses an invisible slime to detect when the player left clicks (I use the entity being spectated as a trigger). It resets instantly so it mostly works well, but sometimes there's this bobbing effect that happens when you stop spectating.
I think it's impossible to get rid of it (if not, please tell me how), so I'm looking for another method to detect left click in spectator mode.