One suggestion for this shotgun. If you do nothing else to it do this one fix suggested by Coyote Caps. At least check it out before doing any other cleaning or changes to the internal parts. Check for a slightly curved/radiused right lifter arm if the problem exists on your firearm. Lifter arm needs to be straight.
9. The right carrier pivot screw hole, is sometimes countersunk too far. Tightening the right screw down, will lock-up the action, or at least cause the cycling of the action to become very stiff. The reason is because the screw threads go through the frame and contact the pivot hole of the carrier. Tightening the screw down, causes the threads to push the carrier inward and will make the action very stiff to cycle.
Cure: take out the right side carrier and countersink the pivot hole in the carrier to compensate for the factory countersinking the frame hole too far. I saw the cause at the factory, when the person doing the hole drilling into the frame, (using a jig), would first drill the left hole and countersink it, then not blow out the shavings. The frame was then turned over to drill and countersink the right side hole, and the metal shavings would fall under the frame, and raise it up on the jig, thus causing the countersink hole to become too deep and when putting the screw into the gun and tightening them down, the threads would contact the carrier and lock it. Because so many of the frames were countersunk too far, the latest models (should) have the carriers already countersunk properly, so those of you with later models should not experience this problem.
PS: Checked the Winchester Shotgun book and it stated that they went to the locking lever for more secure closure because of the new 'smokeless powder' in the 10GA.