Try my guide. How to clean you Blackberry trackball
But stop at step "4". And instead of disassembling the trackball, try to look for any corrosion on the device motherboard.
And try to pull the "spoon look-alike" a bit out. (donxxx8217;t no the name of it
you can also try to press down the motherboard button with a plastic object, to check if it is the scroll that cant reach down to the button, or if the motherboard has a defect.