Fuji Emulsion Losses

[Deepsouth]

I dug out some negs from mid 80s Fuji shooting to scan, and I am upset to find that some (about 5%) have lost bits of emulsion off the negs. These negs have been kept in archival sleeves, but, yes, the sleeves have been piled together in boxes during my various moves. What is strange is that there is no consistency. One neg will have emulsion losses whilst its neighbor will not. And it may be the only neg in the set so damaged. Another set may have more losses across negs. Most of these were handled just once, during printing, and the original prints show no losses. What gives?