Wiring issue

Good day, just looking for a little input…

This past summer a tenant moved her trailer into my park in Southern Illinois, and had it installed in a lot where a previous unit had moved out. Her installer didn’t put it in the exact spot, and her electrician had to extend the hookup. Everything was fine (at least with the electric), until a short time after turning her heat on, when she claims the wires are no longer able to handle the load. Since the wires were already brought to the site, and tested fine at the initial hookup, It doesn’t seem to be my problem. So I guess I have two questions: Any thoughts on what the problem might be? and, in general, is it my responsibility to have the electrical line run from the main meter (at the far end of the lot, maybe 30’ away) to the center of the lot where a trailer is going to sit?