My first thoughts were also that it's not the mic jack and more of a write problem.
Yeah, I second that. If the mic pops in/out consecutively during a gig, you should be able to distinguish some jack noise just before/after the silent parts.
If they are due to bumping around in the venue, you would also probably be able to pin down when you moved or got pushed.
But is sounds unreasonable that a mic plug would pop out 6-7 during one gig, unless you're a very clumsy stealther or in the middle of a moshpit.

So I put my money on write errors.
Like suggested, it could be the end-of-life of the laser.
Pocket lint, moisture/condensation, heat, excessive shake, physical pressure/torsion of the unit are other possible culprits. I ran into most of these myself when MD taping...