Hey Aaron,
We have used thousands of miles of ATR Master tape and have yet to see something like this. Older batches shed more backing than usual for the first ten or twelve passes, but never anything from the emulsion side.
In your photo I see a lot of the deposit on the tape lifter too. My suggestion would be to fast wind it back and forth a few times--or library wind it if that's available--and see what's left on the lifters. If it's still leaving that much gunk, you have a defective reel. If so, ATR will replace it.