cartridge cut off in winchester 61|Winchester Swap Meet|Forum|Winchester Collector

replaced the cartridge cut off with one from jack first. part moves readily in place when pushed with a screw driver. when I load several shells in the tubular magazine they cycle all except the last one when the tubular mag is closed. to get this one out of the chamber I have to pull the tubular mag back and then the gun cycles. the gun will not cycle when the tubular mag is closed. any pointers on what is happening?