Look for rub marks on the fenderwells, on the wood panel. It caused failure more than once before I figured out what was happening. I ended up putting spacers on both the fenderwell and each wheel. I had two ameratrail trailers over the years and both would rub even with trailer tires and proper inflation. I may have had a bent axle or two, they are wimpy on that trailer. Underinflation and auto tires with too much sidewall flex will rub and fail, fyi.
