I think I will do that when all this is settled down. I have only shot about 200 rounds through it and have been trying different oils and grease to see if it improves. But for know at a standstill like everyone else
Where is the lever. That usually starts happening when the locking bolt needs to be rebuilt or replaced. It starts sticking.
If I remember right the KX-5 came out in 2002 as an upgrade to the KS-5 Special. They changed the forend release to a rod and end button similar to a Perazzi TM-1, from the under side release lever, and the went to an adjustable LOP trigger with a wider comfortable blade like the K-80. They added a forend iron block also so you can see it, instead of a steel insert in the wood. They all came with the adjustable rib with the dial adjustment. I believe all were choke tubed and they had an adjustable comb. They also went from a slanted post rib to a straight up post. The changes were I guess an upgrade, but maybe also a marketing change.
Otherwise everything else was pretty much KS-5 Special. The receivers are identical with parts and configuration of the same simplified but very efficient construction.
The pressure to open the top lever is the cocking of the hammer and mainspring.
When you say top lever returns to center, are you saying it is center or left of center? If so, then it needs a rebuild of the bolt. Ottsville will do that for you and an annual while it is there for around $350.
I bought a ks-5 special around 1989 from a dealer in Mayfield Kentucky. Think his name was Kirk. I shot that gun well, good enough to pay for my first k-80 with winnings. Really liked it but wanted a combo set to shoot doubles. Not much recoil and I never noticed any fatigue from the cock on opening feature. Never had one lick of problems and as others have said, it was a pretty simple mechanical design.
I just had an annual and a barrel lug rebuild done at ottsville. If you get the barrel lug rebuild done while the annual is done you save about 60 bucks. The annual was $220 and the barrel lug rebuild was an additional $280. Gun locks up like new! If you want a barrel reblue your looking at $450. I sent mine to phi crenwedge and he charged me about $180 with return shipping. Looks better than new. Thinking of getting a release now that krieghoff is offering 15% off...