It's a big problem and an unavoidable fact. Polyurethane breaks down in the environment and the old polyurethane parts which couple your reel motors to your reels are disintegrating rapidly. Without 'em, you can't move tape! When just one of these breaks, you'll be way "up the creek with no paddle".
Within the past year, the number of calls we've received asking for answers to this problem has doubled. To us, it's the clear signal that the useful life of these vital components is nearing the end.
Here's the answer: Whether or not you need 'em now, order a pair and keep them handy. (seriously, we may not have them when your emergency strikes) The parts come sealed, moisture protected and they'll be ready to use now or years from now.
**Note: the six (6) hole version of the disc, as pictured, may be used on some A820 series recorders as well. Many use a four (4) hole version of the disc. If yours look like the picture, we have exactly what you need.