Here is a trailer hitch-frame problem we had this summer.
We were towing a Saturn Vue with 2002 Holiday Rambler Vacationer...traveling on I-10 from FL to CA...occasionally we would hit a bad spot in the road; some parts of I-10 are perfect, other parts are rough owing to the expansion boundaries.
Near Phoenix (on 95 just off the I-8 bypass) we went over an abrupt low spot (almost like an inverse speed bump); we heard some loud reverberations and decided to have a look...to our amazement we found that the bottom of the frame had pulled away from frame on both sides.
We disconnected the Saturn Vue, and my wife drove it while I drove the RV...we got frame fixed temporarily at a welding shop in Woodland CA; and then resumed our trip (with Saturn Vue in tow) to OR where we had the largest heavy hitch we could find installed on the RV. The new hitch had a long reach to both the top and bottom of the RV frame; the shop beefed up the original frame and the new hitch was bolted to the top, side and bottom of the RV frame.
See pictures of the damaged frame.
First picture, right side
Second picture, hitch position while welds frame and installs gusets to additional strength to the frame.
Third picture, left side
The remainder of the trip (about 5000 miles and return to FL) with the new was trouble free.
On first look the original hitch looked rugged enough; however it was bolted only to bottom of the RV frame and I should have recognized that the hitch should have been bolted to all parts of the rear frame. It seems that as we would drive over bumps the force of the hitch-tow bar system steadily acted to put undue force to the bottom of the frame until it broke away from the main vertical section of the frame. The hitch appeared to be an aftermarket hitch and really not suited for use on an RV.