Valve stem extenders with rubber stems caused two blowouts on the inside dual rear wheels on Interstates in Iowa. Fortunatley, no one was hurt in either situation although I had to buy two new tires in Clear Lake, Iowa.
The answer is metal stems. The rubber ones with the valve extenders were the culprit. Stupid me, I never checked the extenders close enough to realize the stems were rubber. The worst part, the dealer that installed the valve extenders assured me the stems were metal.
Maybe I'm the one who ought to go by Badeye!