Question about my middle assembly

I arrived at the end of the assembly of the middle.
I stopped at this stage :

“Tension bolts “C” should have the locknuts and the bolt heads tightened so they are just touching the plastic. Equal light tension keeps the Z axis perpendicular to the work surface and locks the assembly together.”

juste before to set the tension bolts A and B to square the rail angle.
before continuing I would like to make sure that the tightening of the tension bolts C are correct , but I noticed that on one side, on one of the Z tubes, there are two bearings that do not touch the tube as you can see on the following pictures.

on this side top and bottom touch :

[attachment file=102269]
[attachment file=102268]

while on the other side they do not touch

[attachment file=102267]
[attachment file=102270]

should I still tighten the C-tension bolts?
And if so should I do it now or after having instal the middle assembly on the machine…

thank you

Install it. The middle assembly will flex some of the parts.

ok I will check at the end of the assembly