Here we go again. Has this potentially serious problem been fixed yet? The OP needs to provide much more information about the trailer to obtain any meaningful help. How old is it? Manufacturer? Model? Size? Type of wall construction? Does it even have a generator installed? Any evidence of DIYer installed options? Is the entire metal skin electrified or just a portion of it? Is the frame electrified too? A picture is worth 1,000 words.
Don't assume that all the metal panels on the trailer have a common bonded ground, especially with older units. (corrosion, improper repairs, moisture damage, missing ground straps, etc.) Is the unit old enough that GFI circuits weren't required yet? No one knows but the OP and he/she ain't talkin'.
I've seen it several times where an owner installed an additional towel bar, toothbrush/soap holder, toilet/paper towel holder, etc. where the mounting screws penetrated the hot side of concealed romex wiring and electrified the accessory. Then when touched by hands with bare feet, YOU become the ground! Try flipping the 120 volt breakers one at a time. Does the condition go away? Troubleshooting 101. Get all the information available, then check the most simple things first.
Chum lee