As we have noted, your rifle was manufactured with parts and dimensions there are no replacements for. Gotta work with whar you have.
The Carrier Block is initially started down by the lever and then powered to full down by the spring. Powder residue on the carrier, in the mortise, a burr, a sticking magazine follower or spring problems can cause the carrier to stop and jam the rifle. IF this is a new problem, what was the last thing you did to the rifle???
If you cannot fit new springs or correct the problem by undoing what you did last, you may have to add "positive slam down" whether you want to or not to keep the rifle functioning.
Keeping Uberti rifles, or original Winchesters as "original" as possible is not wise, IF the gun is going to be shot a lot. Overly heavy springs will cause them to "eat" their internal moving parts too quickly.
With out "positive slam down" switching to SlixSprigs will only make the problem worse.
Coffinmaker