I had the same problem with the sensors dropping signals, but in my case, it was not due to the spring holding the sensor. I have a two tire trailer, and had four sensors, so I even swapped out the non-used sensors, batteries, etc., and after a few hours it would drop.
Maybe I needed a booster, but most other systems I have looked at don't require it for a pickup truck running a popup. And even standing next to the trailer tire, with the unit, fully charged, in my hand, it would lose a sensor signal.
So, somewhere in Montana, the system, with the sensors went into a dumpster. I kept the window mount bracket, it worked ok.
Hopefully, the TST system will work better....
Trailer: Lifted 228BH, heavy duty springs and Yokohama tires
TV: 2016 GMC Sierra Z71 4x4 CC, SLT
Spare TV: Two Alaskan Malamutes
Living somewhere in ID; previously lived in Moab UT; previous to that, don't ask!