I work as a locksmith so I'm biased because I only get called for busted ones. No one calls me when it's working fine. But, when I do get these calls I dread them because it usually boils down to me telling them the parts and labor are going to come very close to the cost of a new door/frame. IMO the mechanism is just too complicated and has too many points of failure

Close the door so it latches, put your foot down right at the door, and push the door farther in. Measure the gap between your foot and the door at the new position. Trim a piece of wood to the height of the door frame and the width you measured earlier, rip off old weather stripping, attach wood however you see fit, apply new weather stripping.

I've never done this and I'm talking out my ass but I think it should work. Probably have to adjust your strike plates for the locks to latch and bolt properly afterword

Multi-point locks come with plenty of other problems though

Remove that plate and underneath it you will find the set screw