Carrier/rack problems of the 2015 Ford F-250

The first time it occurred the truck was five years old I was driving on an interstate highway at highway speed, passed over an expansion joint of a bridge, entire truck began to shake uncontrollably, I thought a had blown a tire, but as I slowed to pull to the side of the road, the truck "smoothed out" and I was able to continue on my way. However it happened again two more times that trip, each at highway speed (55-75) and would be "triggered" by small bumps in the road. I took it to a local garage they rotated the tires, did a front end alignment and replaced the steering dampener. Problem continued to reoccur. Has been back to a different garage 4 additional times: tie rod, drag link, track bar joints/bushings, shocks, all have been replaced, however while at highway speeds small bumps in the road continue to induce uncontrollable front end shaking. So far I have paid just under $2500, the problem continues and my mechanic is unsure what is left to try to correct the problem. Online search reveals this to be the "Ford death wobble".