I got some of the old Forte on ebay last month. It was made in 1998 and when i tested a piece for aging, it was fine. I have been searching for this paper for some time as it does split beautifully; while the new papers seem to resist. I know they had to change the formal for environmental reasons.
Someone gave me a 500 sheet box of AZO from the 60"s, and it seems to be fine.
Perhaps the older papers were more stable, or ....................?