Hey.
I have some Deore XT thumb shifters that need a little help. They're on my 1990 Fischer CR-7. I bought the bike new and have always been very good to it, but it does have a LOT of miles on it.

The shifters are stiff to operate.

I've replaced cables and housings, lubed everything, opened them up to check for crud and hard grease (none found). What else can be done to adjust them?

Thank you!!
Flat.