If a valve has become accidentally damaged from manipulation with the lock pick tool or with a file, it may ‘buzz’ or flap, and must be replaced. This may require the reed plate to be removed from the reed block if the damaged valve is underneath the reed plate.
In order to access the damaged valve it will be necessary to remove the reed plate with the blade. This requires penetration the wax (at the tip of the reed) with the blade, and the application of a firm, gentle twist to the blade. If you are careful, you will not disturb the wax too much, and once the repair is done, you may be able to firmly ‘press’ the reed plate back into place.
Though to avoid microscopic leaks, I heartily recommend reforming the wax around the reed palette using a hot knife (warmed on gas stove).
If the valve has been pulled away too far from the reed plate (and does not close immediately with a change in air movement), you may experience a delay in the reed sounding or worse you may even hear a double ‘kick’ every time the note is activated. The valve should be replaced.
If the note goes sharp even though you just filed it to go flat, chances are a valve has become caught in the hole behind the facing reed and is being held permanently open. However, simply inserting the lock pick tool, or applying a ‘ping’ from the blade tool will often free the snagged hidden valve. However, if the problem is actually that the valve has been damaged (by the lock pick tool), then it will need to be replaced.
If it’s necessary to replace a valve, you will need to remove it completely as well as any residue glue from around the rivet and hole. For the new reed, find some flexible textile glue, and apply sparingly to the new valve. In my experience, leaving the glue to dry is not necessary before moderate testing of the reed can be done.
Warning: If you don’t remove the old glue, the new valve may not sit flush with the reed plate, and cause the reed to exhibit strange behavior.
Edward Jay's Accordion Know-How 