You guys are missing something and the reason why I keep putting it off on the RV dealer to fix this. Running an HDMI cable thru the entire length of an RV, is a nightmare!!! You have to disassemble so much stuff (including pulling appliances and/or furniture, panels, etc...).
All of which will also mean; if he ever has a problem in the future, the cheap dealer will most certainly say you damaged in taking it apart & putting it back together.

I would say 'you' fixing it should be a last resort. If at all possible, have the customer make the dealer fix it the right way.
If they won't, then quote time & materials for fixing it and inform the customer the possibility of the dealer giving him crap in the future on any warranty issues, related to what you take apart and put back together.