Toto (AquiaIII) Toilet - Screw at bottom right always coming loose - HELP !

I had hired a handy-man to install my Toto Aquia III toilets. 2 of them. One toilet has no problems, and the other one has a problem with the screw at the bottom right of the toilet constantly working it's way loose within a week after tightening it. When the screw loosens it feels like the toilet sort of teeters slightly. What is happening and how can this problem be solved ? Is it a problem with the toilet and parts or a problem with the installation ? The screw at the bottom left of the toilet holds perfectly.

Help, Hilda

With installation.
He should have shimmed the bowl if it was rocking, and then caulked it to the floor.

Jamie has instructions for the Aquia here

IOW, the toilet MUST sit flat and stable on the floor on its own...the anchors hold it in place, but don't and can't hold it in place if it can rock. He may also have drilled an oversize hole, and the plastic anchor isn't gripping. As Terry said...shim it. Also note, if it rocks much, the wax seal is probably compromised, and it should be reset with a new wax ring. The wax isn't a spring, and if you compress one side, then lift it, it doesn't rebound, and may produce a crack in the seal. Now, the wax is sticky, but that doesn't guarantee it won't split.

Jamie has instructions for the Aquia here