Anyone who can explain why yanking it out of the sled cures the problem and switching the unit off doesn't?

Because switching the unit off doesn't actually turn anything off. It just puts it in standby mode: It pauses playback, spins down the drives, and turns off the display.

Question: In both of your cases, do you have dual-drive systems? And are the missing songs on the second drive?

Is this just a loose-jumper-on-the-second-drive problem?

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Tony Fabris