Searching for adjusting multipoint morerise lock
(1) 82-265 : Multi-Point Mortise Lock with Face Plate, 11"
(1) 82-249 : Sliding Glass Door Multi-Point Keeper
This has happened before. First, there is a small, flat-head adjustment screw between each hook and the main installation screw. If you turn those, the hooks should extend or retract. If that doesn't help, another thought would be to space out the keeper with washers to try and give it more depth. See if that enables the anti-slam button to properly interact with it. Let me know how you make out.
I will try more spacers but with the one lock only partially extending, I do not know if more spacers will resolve the problem.
Mike
The screw in question definitely looks to be hidden by the door frame. Considering you said one hook sticks out further than the other, I definitely think that adjustment is the primary issue. You can always just remove the mortise, adjust the hooks as necessary, then reinstall.