Ideal 5221 blade goes up after a while

Hello, a few months ago I got used ideal 5221. When I fine adjust blade depth with screw +- after about 30 cuts blade starts to go up and again need to adjust depth with turning +. It cuts fine, but always need to make it go deeper as it constantly moves up again. Is it normal? Blade is tight no loose bolts

 

Are the three eccentric knife setting screws firmly on the blade. They are located above the knife bolts. They help keep blade from moving

 

I have changed the blade to new and the problem is gone. The old one knife was 82 mm width (recommended minimum 83 mm). I think it was too short for adjustment screws to keep it in place.

 

I would like to know if i could adjust clamp pressure (binds 3-4 pages on top of coated paper, specially if it fully printed), also there is other questions if i can regulate and how clamp high that it could hide the blade, also there is three small buttons on the left side of cutter under the table, but they seems dont work etc..