You might have a couple of things going on here. If the sparks from the lock are small and bright white, the frizzen is likely too hard. If the frizzen shows little or no wear, and in fact almost looks polished, the frizzen is too hard. The cure is wait until the wife goes shopping, and put the frizzen in the oven at about 400 degrees for an hour. Then let it cool naturally.
Modern flintlocks, that are patterned after early locks without a roller, often don’t allow the frizzen to cam over far enough to avoid bounce back. The rolller on a roller frizzen almost locks up the frizzen in the open position. This is not true of the earlier nonroller frizzens. In fact if you look at a bunch of early rifles, and muskets, that have early locks, you will see that the frizzen at rest lays way more forward than most modern locks. This prevents most bounce back. Recontureing the foot of the frizzen will allow the frizzen to lay more forward at rest, and solve most bounce back issues.
Hungry Horse