8100, some keys dosn't work well
 

My 2 years old 8100 is still in perfect conditions but some keys of the main keyboard sometimes must be pressed hard to work fine, specially the hang off (red phone) and the "op" (qwerty).
I have taken apart the 8100 fully and I cleaned with a contact cleaner the surface contacts of the keyboard membrane, because thi seems to be sealed.
This helped a little but not solved the issue.
There is a way to clean contact under the membrane?
May a new keyboard help?

Probly cheaper to buy a new phone

Taken apart again re-cleaned with more contact cleaner, now it works better