Trailers having running gear problems, has been an issue for the 52 years, that I have been driving the Alaska Hwy. As much as I dislike government regulations, in general, the ones for vehicle safety on cars, trucks, vans, etc. have prevented many problems for travelers, IMHO. As far as I know there are no government standards, and never have there been, for the undercarriage of any trailer, be it a pop up, a travel trailer or a 5th wheel. It is up to each builder to decide what they feel is acceptable to put under a trailer and then sell it to a person. If a person stays within the specified gross vehicle weight ratings as specified on the data plate, usually not too many running gear problems will occur, from what I have seen.
While over the years, I feel they have many less problems than they once did, they still have way more problems than do the vehicles that come under the US or Canadian government set of standards. Somewhat based upon that, we have made most of our trips in Class Cs, slide in truck campers and Class As. Made one trip with a popup, about 1969 and broke a spring shackle off the frame hitting a pot hole, back before the Alaska Hwy was paved. Drove our 5th wheel over it without problems but then set it up as a permanent fish camp on the banks of the Kenai River where we owned a river front lot. I had to replace the spring shackles on it as well, but due to turning it too sharply, IMHO and putting too much pressure sideways on the axles.
We currently have a 5th wheel which we enjoy greatly as a destination vehicle, but it has so much room to stuff items, and with me being part pack rat, I have to be real careful not to over load it, when heading out west on a trip. It hasn't gotten to go to Alaska yet and it may not. Our Lance Truck campers have made the last 4 round trips. It would probably never do for me to own a toy hauler, as much I like the looks of them. Way too much space for me to pile junk in it. LOL