I read that you have it on the 3rd level of your rack. is this back or belly heat? and no tape on the probe. is the probe touching the flexwatt? you need to tell us more details on the location of the probe to the flexwatt.

my probe is about middle of my rack.(this refers to the height of the rack) metal taped to my flexwatt where my tub doesn't come into contact. thats the belly heated racks. the back heated racks, again about middle of the rack,(again height of the rack) the probe is taped to the floor of the rack about an inch away from the back heated flexwatt. the tub doesn't touch this setup either.

if your probe is secure correctly, then it sounds like you have a problem with your thermostat and need to contact the vendor.
the thermostat controls your flexwatt no matter how hot it can get, its the thermostats job to prevent this. the only time it can be a flexwatt problem is if you're getting no heat when used with a thermostat. the tape on the ends of the flexwatt is good. mine is also taped. and yes you need to have some kind of control on the flexwatt until you get this corrected. so use the other thermostat and keep an eye on the temps with a temp gun or something that you have.