Originally Posted by Dave1096
That clamp is called a romex clamp, and your problem is not fixed by loosening the clamp. When that clamp was originally over-tightened the sharp metal edges on it cut through the insulation and grounded-out either your hot or your neutral. When your electrician loosened the clamp he broke that short to ground, but the problem still exists and is a serious safety issue. I can't believe your electrician didn't mention this to you because this is a pretty easy issue to troubleshoot. Replace that run of wire, don't over-tighten the clamp, and you're good.
Wanted to follow-up. I did replace the orange wire to the 30A outlet. Afterwards, I peeled-back the insulation where the romex clamp had pinched it to see and of course Dave1096 was absolutely correct. The neutral had pinched through the insulation and was grounding to the romex clamp.
Would this have started a house fire? I'm glad I will never know.
Thanks for the fast feedback guys.