Can't understand what you mean by "pushing it". You shouldn't need to "push it". I find I get by with just a touch of the thumbnail or fingernail is enough to activate anything.

Anyway, to the problem. There were some issues with some screens (pre PR1.2) where the top left and the extreme right of the screen were were a bit dull in the sensitivity dept, thus needing a bit of extra pressure, but I'm guessing you're already running PR1.2.
Another problem that was displayed by some screens was that the metal bezel actually warped/twisted and worked loose, I'm not sure what the fix was in this case, but to check for this, slide open the screen and check the gap between the bezel and screen back-plate. See if the gap is the same all the way around.

No harm in contacting Nokia themselves for advice though.