Wista 45VX stiff focusing knobs and back swing

I've received a Wista 45VX today and I'm really pleased with it. It seems really well built.

But I'm having some problems using it:

1) The focusing on my camera is very stiff. I can barely focus using only one knob, I need to use both knobs to move the rack. I checked the three little locking tabs and they're all open. Any suggestions? Is there a way to loosen these knobs or should I put some oil on them?

2) I can't swing the back. I push the little lever down and I can't move the back at all.

Here are some pictures of the knobs to illustrate my questions.

So yesterday I found the solution: I loosened the screws (marked on the picture below) on both knobs and now the focusing is very smooth.
I think it's the same for all metal Wistas.