Im convinced probes get ruined by prolonged contact of the prob directlly to heat sources. Years ago i used to attach the pribe right to the flexwatt and i went through 2 probes on my helix. I quit doing this and use a dummy tub in every rack bow instead of attaching the probe directlly to the heat and never had an issue since and its been about 10 years. I may be wrong but its the only thing i can think it was