Doc Huckleberry

Interesting problem with my Uberti 1866 carbine. Tips on both lifter springs broke last year. Sent it to the fellow who’d fixed both my SxS shotguns, along with a Pioneer short stroke kit. He fixed the two springs, got a bit concerned about the mods for the short stroke kit and sent the gun back, with the assurance that he’d tested it. However - the first cartridge you feed in comes right out the back of the carrier and jams the mechanism. Tried a new aluminum carrier from Pioneer, and a set of their springs - no luck, no joy. I’ll note that the carrier, new or stock, now comes about 1/16” below the frame with the lever closed, which it did not before Any suggestions? Thanks! Doc Huckleberry