I wish you luck with it for the lad.
My local gunshop bought a load of Kofs in various calibres (but not 28 gauge).
A lot of lads in my game syndicate bought 410s from him because we have a charity 410 day every year. The proceeds of which go to a local kids hospice. It's a couple of grand each year.
Unfortunately most had missfire problems, which was resolved by shortening the firing pin spring, this was only on 410 variants by the way. So if it starts playing up maybe suggest to the rfd a probable cause and fix.