There was a report on a NYC audiotape archive just now.
Mentioned was a common problem of tape flaking and one
last ditch solution was to bake the tape in a convection oven
for 24 hours, presumably to re-seat the oxide into the plastic.
Sounds like the temperature has to be exactly right.
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Google "Sticky Shed Syndrome"
Common problem with hydroscopic decomposition of the tape binder.
A temporary solution is to dry the tape out by baking.