I seem to have fixed the bothersome bog seat that snaps shut if you open both bits. Turns out there's a tightener on one side. You can't adjust it fore and aft for a more reclined seat angle so it has to work on resistance. Tighten that up and now it stays upright instead of trying to snap at you like a demented turtle.
Will make cleaning it a lot easier as it was a bit tiresome getting a bruised arm if you weren't keeping an eye on it.