Be aware that when the TST beeps that you've lost a sensor, that sensor may not have been in contact with the monitor for over an hour. It can take an hour or more of non-communication with a sensor for the monitor to finally beep. This is a known issue that some have with the TST system.
This last trip I happened to glance down at the monitor, I rarely watch it since I rely on the alarm, and noticed that I had one tire that was 10 psi lower and 5ยฐ cooler than the rest of them. We had left the campground about an hour earlier and all sensors were working at that time. While I was wondering where to stop and check things out, the monitor beeped indicating that a sensor had been lost. It was the one that showed the low pressure. I moved the monitor around and it picked up the sensor and showed the same pressure and temperature as the rest of the tires. It does happen.
Howard and Peggy
"Don't Panic"