I have two Herpstat 2 thermostats and have no issue with either one (save for the time my older one went into system failure due to a power surge - resetting the device fixed the issue and per SpyderRobotics it was still safe to use if it reset appropriately). It should not be having an issue with the probe or power port on either side. That is really unusual.

Did you purchase them from SpyderRobotics or a third party seller? I'd contact SpyderRobotics customer service either way. They are top notch and respond quickly.