I noticed the same thing too. This happens to all Laminar’s aircraft on 11.35r1. On an approach, after passing the IM, the beeping stops, but it starts up again over the touchdown zone. And as you’ve said, beeps while waiting for takeoff as well. Very irritating.
For the meantime, you can assign a key to the command “Mute marker beacons until next marker is received”.
Perhaps you can file a formal bug report to Laminar.