Donuts, anyone? Seals, I mean...

[Nomadicflyer]

Question: I have a donut exhaust seal that keeps blowing out on me. I thought the nuts were backing out, because they would be missing, so I put in some bolts with safety wire. The bolts stayed put, but the exhaust seal still blew out. Several times. Is there any other reason for that to happen beyond an alignment issue between the headers and the Y pipe? My next step was to cut off the flange and put a new one on, with a fresh alignment.

1972 C20 350

Thanks!