John Deere SX85 - Gear shift frozen

I have a 1996 JD SX85 in otherwise excellent condition.

Last year, when starting the mower in neutral, the shift lever would not immediately change gears.

After some jerking and banging, I could get it into gear and as I rode it the gear changes became easier.

After winter storage, the mower does the same thing, though now I cannot get it out of 1st gear.....at all.

Any help appreciated.

Thanks,

Sarge