Mills nickel slot erratic payout & last wheel slows first

[nickleslot]

Hello. My first time on this forum and interested in advice. This Mills nickel slot has been in our family for decades and it has been setting in a heated basement for that time. At first it would not payout at all but now (after WD 40 ) it pays on the 2 cherries and whatever but not on any of the high payouts. Fingers look correct in disc slots but nothing dispensed.
My 2nd issue is the 3rd disc/wheel slows down much sooner than the first two when making a pull. I have very low brake tension on this wheel. When the unit is out of the case, this wheel cycles and stops correctly.
Any advice is appreciated; I checked YouTube but limited on the depth of certain problems. Thanks!