Player able to build inside of J6 rock

Player able to build inside of J6 rock. Please reply back if you figure out how this is done or how I can fix myself in rustedit

I checked this rock in the editor and in-game and couldn't find any holes through which a player could get inside. It looks like they somehow managed to place a sleeping bag inside and got in that way. A long time ago, Facepunch added a parameter that prevents building inside rocks, but back then it caused issues with building at custom places, so I advised disabling this parameter. However, it seems there is no need to keep it disabled anymore. You might still have it turned off since then. The parameter is antihack.build_inside_check