Done a few years back this is a sequence of photos that documents the restoration of a mahogany ended 30 button anglo that had many common woodwork defects. These had to be put right before there was a chance it would play properly.
The action boards had several shrinkage cracks like this one. These are common, especially in cheaper instruments made with badly seasoned timber.
Shrinkage can also lead to failure of glued joints here leading to large gaps opening up between the action board and the frame.
First stage in repairing the cracks is to glue in slips of wood, actually I used pieces of veneer for these cracks...
... and slightly thicker pieces for the open joints.
Buttons before and after cleaning. The top row of buttons are as found with a thick accumulation of dirt. The bottom row have been cleaned by scrubbing with detergent solution.