I have the 507 TST, bught with the flow through transmitters
my issues
a valve extender didn't play well with one of the sensors...sometimes it would work , sometimes not...it wasn't depressing the valve stem (or maybe it was depressing it too far and conflicting with the transmitter plugging the hole)
The factory batteries in the sensors will leak. Change them early.
I had some show signs of water damage. i suspect the o-ring seals may have failed prematurely.
Factory was very responsive and replaced some of my transmitters.
I have started to replace with non-flow through models
last thing, take the transmitters off if you're going to park and store for any length of time, kills batteries. So I pretty much take them off any time I store since it's usually a month or more between trips