PERHAPS it stops writing to the file too soon? If you've closed down Poser before the PZ3 was fully written? Or if you're using an external hard drive and that one isn't plugged in? Poser still references stuff in the PZ3.

I'm guessing wildly here, luckily I have never seen it happen myself.

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.