Ground voltage!!

Here, get this and see what it tells you.  AFAIK it is the cheapest 3 prong tester which has built-in neutral to ground (N-E) voltage measurements:

Reverse Neutral and Ground/Earth is one of the common problems in wiring, would it be at home or at a factory.  Outlet checkers as shown above don't test for this problem.  There are ways to test for it, but you have to be quite familiar with electricity - don't try to do it if you aren't. 

Get a cheap and a physically small AC clamp meter either on Amazon or at Harbor Freight (or wherever you go to for such things).  Precision isn't that important here - settle for the cheapest one.  In a distribution box (you may need to take the protective cover off) measure currents on Live, Neutral, and the ground wire while you have some loads at your house on.  The currents on L and N should be ~same; there shouldn't be any appreciable current in ground wire - just a very few mA.  Such N-G reversal can happen just about anywhere in the long connection from your distribution panel to your outlet.  There are plenty junction boxes with twist-caps (the usual suspects - not the caps, but the miswired connections).  Your outlet may be miswired just as easily. 

Again, you need to be quite fluent in dealing with all things electrical to do such test. 

@lewm , I really like herring.

More stuff posted for this poor chap.

Like this by @vk_onfilter   "Again, you need to be quite fluent in dealing with all things electrical to do such test."

Why doesn't OP just get a qualified electrician for C*****s sake????

Not rocket science.  AND END OF STORY

Happy ending.

Mijostyn, I’ve always wondered about the origin of the phrase “red herring”, but it does appeal to me. The only time I ever drank so much that I barfed was after also eating canned herring. That was in college, and I haven’t eaten canned herring since that incident. Nor have I ever gotten as intoxicated.