Your description of what is occurring is quite good actually. When you move the lever all the way forward, the bolt is all the way back and the new shell is pushed (from the magazine spring) onto the elevator. That has nothing to do with the extractor. The extractor issue would come into play once the bolt and lever were closer into battery.
With mine, the round nose were just a tad too long, even though they were within the OAL specification and would rub or bind on the the face of the receiver between the magazine and the chamber. That was where the ammo is critical because you have to ensure that the casings are 38 Special and/or 357 Magnum. (the difference in the casing is only 1/16"). If anything else is used, then it will not function properly. Further, if the shell casing is too short, the movement of the elevator could put it out of round and cause a jam in the chamber.
In my case, it was a piece of lead that caused it to jam up. I could unjam it with the use of the lever, so it was not big deal. The lever, depending on ow much force you use, exerts an awful lot of force and it can cause issues if the ammo is not right.
The thing about the spring, also leads me to believe that perhaps your ammo may not be quite in spec. You see, the spring (with only two or three shells in the tube) is nearly fully extended and does not have as much force pushing on the shell (on the elevator). The next in line, if the previous is too short, will have it's rim protrude too far and perhaps even on the elevator (which will also cause a jam).
I now set my round nose a little deeper and have not had a jam with those since. I do however, use the flat nosed rounds about 95% of the time.