It was from using vit-e oil as the base liquid, found exclusively in one individuals homemade THC carts (although others are suspected as having the same mistake). The media really dropped the ball on tht one.

You also kind of dropped the ball on providing a source.

Find it yourself, a single Google search will find that he's correct about the vitamin E

A deeper dive will find that it’s not conclusively proven yet, and I can’t find much evidence for the “one guy’s fuckup” assertion.