The scratching is normal. The way a flintlock sparks (or a flint-and-steel fire starter) is by scraping tiny shavings of metal off the steel or frizzen. The shavings are heated to incandescence in the process, and, falling upon the priming or tinder, ignite them. The flint also flakes away in the process, so needs to be replaced or re-knapped when it is no longer capable of striking sparks from the steel.
Because the steel must be hardened and tempered to a specific range for proper function (which is why an improperly hardened piece will not produce sparks, or do so only weakly), and because the hardening may only be fairly thin on the surface of the steel, the steel or frizzen can also 'wear out', and fail to spark until re-surfaced or re-hardened to provide proper material for the purpose.
mhb - Mike