My trailer used this door shown below and my fix back then was to use a piece of 2X2 foam around the cable to seal it off when I slide down the cable hole plastic cover.
I cut my foam strip from one of the house window air conditioner foam strips available from WALMART-Lowes. I use these same strips all around my tent beds in my OFF-ROAd POPUP trailer to seal up air holes everywhere.
Roy Ken
My Posts are IMHO based on my experiences - Words in CAPS does not mean I am shouting
Roy - Carolyn
RETIRED DOAF/DON/DOD/CONTR RADIO TECH (42yrs)
K9PHT (Since 1957) 146.52M
2010 F150, 5.4,3:73 Gears,SCab
2008 Starcraft 14RT EU2000i GEN
2005 Flagstaff 8528RESS