first, if you've already confirmed that your 'ems' is saying everything is fine, then BYPASS it and run directly to the outlet - chances are your ems doesn't like the GFCI outlet, or a combination of the RV's GFCI outlet and the shower power GFCI outlet - sometimes they don't play well together.
I've used GFCI circuits with no issues, but I also don't use any ems to get in the way.
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