While this is a long shot of epic proportions, I would contact Ruger/Marlin and explain the situation and just see what their response is.
https://www.marlinfirearms.com/
BTW, out of curiousity, Is this a JM Marlin from 1988-89 ?
Or a Remlin from 2006?
I have a 41 Mag JM Marlin from 1988-89. The rifle had less than a box of ammo through it, when I got it. I had some FTE issues. While it's not mentioned in the link below, the majority that FTE was older worn W-W brass. Anyway, the problem was the barrel shank's extractor seat. Maybe have a look in your gun, to see if that was poorly machined also.
https://castboolits.gunloads.com/sho...ues-need-HELP-!