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All the above advice is good, but before you go to a lot of trouble, try a quick test: Turn the breaker off, then scrub the plug in and out of the receptacle a few times. Sometimes the contacts (in this case the ground contact) in the receptacle get corroded and lose connection. That can happen with temperature changes. Then see if the code on you surge suppressor clears. If you have any adapter in the line, scrub those contacts also.
This is just a troubleshooting test - if it clears the problem you probably need to replace the receptacle for a permanent fix. Use a good quality receptacle.
Amateur Radio WA4GIY
2015 Montana High Country 305RL
2013 RAM 3500 4x4, crew cab, long bed, 6.7 CTD, Aisin trans.
CGVW 20460 Lbs.