I've never had one pop off when de-capping, seating is a different matter.I had one go off while decapping once. It really was no big deal. At that point, there is no powder or bullet in the equation. It was just a cap going off. Not even really that loud.
My older brother and one commercial reloader that hits the shows like Tipton, Muncie and the shows up North have had primers pop running Dillon 1050's,
The Commercial loader also had bad housekeeping with cleaning up spilled powder. He will openly tell you all about how stupid it is to run progressive machines with raised anvil primers, no lid on the powder measure and then add poor powder cleaning. He just about burned his shop down. He sold blackened reloading equipment for months after than fire.