None. Ever.

I've used perhaps 40,000 Fio 616.

Only thing that won't light reliably is Titewad. Fio 616 is better with a flake powder than with a ball powder.

I finally had one misfire a few years ago. One in 40K is pretty good, and it apparently had no priming compound.

That said, all my Fiocchi primers were/are a few years old. I have not used 'current' manufacture Fio 616's.

"The price of good shotgunnery is constant practice" - Fred Kimble