The Uni-T UT25A/B transmitter unit is defective for circuit wiring checking. 

My UNI-T transmitter for UT25A/B Circuit breaker finder that also serves the dual purpose of an outlet receptacle checker that it is wired correctly giving me wrong reading. Here I show it in comparison to my older Sperry wiring checker and also to my Klein Tools outlet tester. Both the Sperry and Klein Tool correctly shows the outlet is wired correctly, but the Uni-T reads open ground when tested on same exact outlet.