At least your thinking about replacing it. I can't begin to tell you how many times I have replaced this stuff after some junior tech know it all put the amp back together with the same burnt up cardboard left inside like it had no purpose
Keep up the good work my friend, and if the stuff I suggested looks too thin its OK to double up on this stuff. As it serves its purpose to equalize the crush pressure across the devices, and to allow for different heights of the assembly.
Keep up the craftsmanship, perhaps we can save this industry yet...