Hit a bump at approx. 55mph going into a curve while pulling a loaded car trailer. The unstable 4-link rear suspension combined with the air bag suspension system created/allowed/exacerbated trailer sway that caused the trailer to ultimately jack knife into a fence off the highway. This endangered myself and two oncoming cars in the curve. Driver skill and shear dumb luck prevented death to any/all on the road. Poor/unstable rear suspension engineering caused the accident. The air bags did not deploy and I do not recall the seatbelt locking up. Stellantis subcontracted Bosch Automotive Service Solutions (CASE # 91832257) to examine the truck. The inspector could find nothing out of "spec" or alignment, but was able to reproduce and experience like symptoms (and was visibly unsettled) during his test drive. Stellantis, not two days after receiving the Bosch report, denied all responsibility

- Pahrump, NV, USA