IMO plated bullets offer less protection then the often miss-called "bare lead" wax coated bullets.
The plating or wash is very thin and IMO mostly for looks. Where wax, talo coated bullets offer a thicker layer of protection.
I have never had this issue myself, all I run is CCI Blazer 525 Value paks.
I do remember someone else posting a photo like this is the 1st 795 thread. Might want to go thru it and look (lots of pages to sort thru)
I would would check the barrel for bulges on the outside.
It's possible that you had a squib and then dislodged it with the next bullet but in doing so bulged the barrel, giving the lead a place to attach.