Originally Posted by TimPa
i don't think it is recommended to push the button on non-gfci protected circuits, which is where you're problem may be.
I tested a non-GFCI receptacle, pushed the button, then tested the receptacle that showed hot/ground reversed this morning, and it tested ok.
There is a freezer on the gfci circuit, in the basement. Maybe it was running or started up when I was testing this morning and caused the reverse test?
Edit - I just read the instructions again, and it does say to unplug all appliances on the circuit before testing.