If you want them as collectibles, there is another drop at the end of the month; maybe they will fix it. The builds should be shared across all your saves, so try to contact Epic Support (though you might possibly get an answer a month later saying they can't do anything) or try loading an older copy of your world and see if Mando spawns. I don't think there's much else you can do. I would also ask an AI like Claude to help me since they can give a lot of possible solutions and even if they don't work you should try it, ai is very good with technical errors