Newbie from Greece / Athens - ACE 737 yoke question

[jaguara5]

Hi guys!
Newbie here from Greece!
I fly the fsx pmdg 737ngx and my hardware setup consists   of the ACE 737 yoke and the recently received
737 TQ from cockpitforyou.com . 
I had  no problems so far, however from yesterday the yoke is much more stiffer in the aileron axis,  still 100% functional.
Pitch axis is normal. In the upper back side the yoke has a screw for aileron stiffness adjustment (and 2 in the base for pitch axis), when i received the unit 6 months ago i had adjusted  the resistance in all  axes to be soft.
I tried to readjust the aileron stiffness but i can't find any screw (and i don't remember how the unit   originaly was). There is only a hexagonal  hole, which rotates with the yoke movement.  If i put an  allen key in, i 
can move the yoke to left or right. I have found in the floor a very small
allen screw, which i don't know if it's a missing part, i can't screw it in
the previous mentioned hole.  Has anybody an idea, of what is going on ?
Thanks in advance
Makis