Any idea what kind of bug this is?
When I was working in Chicago doing kitchen and bath remodeling in high-rise condos every toilet I removed had 4 big roaches (2 inches long) nose to tail just below the wax ring.
There was always a 5 second delay before they'd be like "Hey WHO turned on the lights" and would run down the toilet drain ?
I'm guessin the drain/sewer system was loaded with em'.
You should try to get some poison or smoke into them plumbing pipes ?