Sony TRV-900 audio dropouts

[R Underwood]

A few years ago (maybe five), I bought and have been using a
Sony TRV-900 miniDV camcorder.  It worked great until about
6 months ago, when I started to notice audio dropouts during
playback.  The dropouts are now so frequent that output is
unlistenable.  Clues:

* I have used only Sony tapes in the camcorder.

* I have never taken the camcorder for maintenance.

* When I print to miniDV tape from FCP, the tape itself has
  fine audio.  (The camera drops different parts of audio on
  repeated playbacks of the same tape.)

* Playing a Sony cleaning tape repeatedly seems to help,
  but after a few seconds of clean audio playback the audio
  dropouts creep back in, increasing with frequency as I play
  more of the tape.

Does you have any troubleshooting suggestions or
possible diagnoses?

Thank you,
Rebecca

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