Sorry to hear you have had problems with these. I have been using them for almost 20 years with no issues. The exception being that the battery died and it was not one easily gotten, that is why I switched to common batteries detectors.
I did have a place it would tell me what I wanted and that was in an old house with the neutral switched and no ground in the box. I build a very long test probe I could connect to a ground to find the hot side.
Good Luck from Columbiana, Alabama
Maurice Turgeon, Hidden Content