The original board we replaced just had a defrost issue... I don't suppose a thermistor would cause a defrost issue would it?
It absolutely will cause a defrost issue. If I have one not defrosting due to a bad board and there is not any obvious damage to the board I'll replace the evaporator thermistor too if its the common-to-fail early stlye just to cover everything. Of course if I know the thermistor is the problem I'll only replace that but if its the board I'll eat a few dollars on a thermistor so I don't get a call back in the near future with a customer saying its the exact same problem and I sold them an expensive board they didn't need if its not defrosting again.