^^ I'd suggest you are placing too much faith in external safeties.
I dont recall how many times I've found a Colt 1911 with the safety off when it was in the holster, but it has to be a dozen or more easily. This is in 4 different Colts I've carried (all factory parts), and several holsters, mostly Bianchi thumbreaks. I finally figured out that the gun blank they molded the Bianchi holsters on had the safety OFF and the mold of the holster actually puts pressure on the safety to take it off when carried. I've also found the safety off when carried in a holster that had no leather close to the safety.