Did u have them hanging inside the tent? I have 4 total and only 1 i have ever had issue with is the heat only unit! Its the one used for reptile aquariums cuz i got it free! They have replaced it like 4 times already and its still only one ever had problem with!
The first two humidity and temp were in the tent the replacement models were not. Was advised to hang outside the tent as high humidity could affect them. The irony of a humidity sensor being effected by humidity...the highest the humidity in the tent was 70%ish. Hell, the humidity is higher than that anywhere in the south!