The only way your trailer sees the frame grounding is through the three wire connection you make to your house...
You really have to respect this as what may just be a tingle shock to you might have real bad results to someone else or a small animal etc... UNPLUG your cables until you figure out what is wrong...
Two things to check... You have to be sure your are using all three conductors. Sometime folks cut off the GROUND PIN on the extension cords for some reason.
Then you need to check to see if the receptacle is wired properly... I use one of those CIRCUIT TESTERS from LOWES plugged into the 120VAC Receptacle in the house side... It will tell you the ground is not connected properly.
I also always use a 10 gauge (10-3) HD contractor grade extension cord... However a 12 GAUGE will work also. The smaller gauges red/orange 16-gauge cables from the WALMART is too small and will get hot on you especially if you are using your air conditioner.
I also always use the RV30A-15A LONG DOGBONE type RV adapters that looks like this..
Using the small round adapters would always get hot for me and eventually will burn up your good cords...
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