My version of axle support

And useless to the end user. This is a warranty to the OEM (FR). Also it excludes overloading and unreasonable use.....as determined by Lippert in their sole discretion. So, FR would have to want to take on your case, and be willing to attempt to prove that your axle wasn't overloaded or encountered unreasonable use (like say hitting a curb). Good luck with that 

Basically, there is no joy in Mudville with warranties like this for an individual user. We can let one of our resident laywers weigh in but I'd guess you'd need to show a pattern of similar failures and iniitiate a class action suit to get any traction. 

And pretty clearly the axles aren't failing at loads below 3500 lbs just sitting there. The argument would be what is a reasonable safety factor to apply to an axle rating. I've seen numbers in the 2.5-4x range in the vehicle world to address bump loading, but it doesn't look like there is a single accepted standard. What the indiviudual manufacturers use internally is a trade secret. I think the Lippert axles as used on the rPods have a load factor of around 2.5 to 3.0, so toward the bottom end of the range, but not way out of the norm. Just my $0.02.

But.....

The weakest points are just outboard of where the axle tube is attached to thr frame supports.  The tube gets pushed up under load at those points. I might be missing something but I don't see in the pics where you have reinforced those areas.