I've heard of it happening on occasion. You're fortunate the axle didn't move out of alignment and do some damage. The trailer shop guy who replaced my boat trailer springs informed me there's a significant difference in price and quality between Chinese and American spring steel. Chinese-sourced springs last about three years in a saltwater environment where American springs last much longer. I suspect there's a parallel with towed RVs because I would think the mfgrs. are sourcing the cheapest springs.
--2005 F350 Superduty Crewcab, 6.0, 4wd, short bed, 3.73 gears;
--2016 Montana 3711FL, 40'
--2014 Wildcat 327CK, 38' SOLD