I've never had any problems with my ftss2. I've got 2 systems on brew buckets. Have been able to cold crash down to 35 with no freezing issues, as well as maintain fermentation in colder conditions with the heat pad.
The heating function works best when theres movement of the wort through fermentation. It will work without fermentation, but its slower.
There are limits to the system though. Dont expect to maintain 65 degrees with 30 degree ambient temps. Many people dont know that you can plug the pump and chiller coil into the heating side though. You can use an aquarium heater inside a cooler to heat water, then pump warm water through the coils. That works much better than the heating pad.