Tough diagonals on square-button Famicom controllers

[lobdale]

So I got a square-button Fami in the box today, and everything is in really great shape, but I have noticed while just testing out the system (with Contra), that the diagonals (upper left, upper right, down left, down right) on both controllers are really hard to push!

If I push really hard, they'll register, but I need to hold them down pretty good.  I took the P1 controller apart and it looks really good, the rubber under the d-pad seems springy and everything.  So I guess what I am wondering is, is this a known issue with square button controllers?  Should I try to pick up another set of controllers or swap in some rubber from a different controller and try it out?

Post Merge: March 05, 2013, 03:56:13 am
(I guess I spoke too soon, I swapped a rubber from a different Famicom controller and noticed it was much improved.  But the square button controllers have black rubbers inside while the round button ones are white!  I guess I'll just keep it stock since I won't use it as the "playing" Famicom anyway)

Is there any way to "service" controller rubbers outside of just replacing them?