Sounds to me like you need a selection of things to try - before you buy a new frizzen, that is.
1. Try REAL English Brandon flints of the correct BB size.
2. Try an artificial agate flint.
3. What are you using to hold the flint in the cocking piece? Leather or lead? Sometime using leather means that the edge of the flint vibrates against the surface of the frizzen - perhaps judders is a better word - rather that the correct scrape the produces the sparks.
4. Not trying to be a PITA, but I'm assuming that the flint IS right way up?
Last but not least, frizzens DO wear out, especially if they were, ahem, not very good to begin with...
tac
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