You can damage the frame with any hitch/pinbox. I have two broken welds behind my pin box, but I don't blame them on the Goosebox. Poor welding, bad roads, and off road travel are all part of the equation.
The Goosebox may not have helped things, but your individual usage has a lot to do with it. There are thousands of people who put tens of thousands of problem-free miles on Gooseboxes, or even gooseneck adapters, without issue.
In the process of welding a bunch of guessets and bracing on now. Keeping an eye on your trailer and looking for small changes each time you hook up will go a long way to prevent major damages. Things happen, and I just happened to think the trailer was sitting a hair closer to the bed rails than normal a week ago. Pulled back the trim to find this:


In this case, Lippert used inverted angle and only welded one leg. I think the angle is too thin, and the welds needed to be on both legs, to survive what I ask of them - regardless of hitch. This was a ticking time bomb even with the stock pin box and TrailerSaver BD3 I ran before. If anything, the Goosebox just made it happen sooner.
Damages, often with unknown causes, are a fact of life when you RV. Some things are quick to be blamed, even when they're not the root cause - there are multiple intertwined factors at play.