Gunut;
Do you have to hold the lever over while closing the gun? If so I would guess a part is either missing or broken. There are a lot of doubles on which the lever does return to center with no latch, but upon closing the lever is cammed to the right by the bolt. I would not say a top lever gun has never been built that "Requires" holding over the lever, but they are few & far between.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra