Hi JMule,
Welcome to ALR. The lock cycles fine out of the stock, but the frizzen won't open fully when the lock is installed in the stock. With the lock in the stock, can you open and close the frizzen by hand?
Sounds like to me, something is rubbing somewhere. Maybe you could apply inletting black, candle soot, etc., to the lock works, install it and cycle the lock, then look for tell-tale black smudges in the lock mortise?
That's my guess. Somebody here will know.
-Ron