it's some kind of triple bar version of an 809, so the 809-B paperwork would be appropriate.
you can find paperwork in
https://bingo.cdyn.com/slots/if there's no model/serial number plate on the side below the handle, then see what codes are stamped into the slotted metal reel index discs.
payout issues kinda depends on what you mean by random. Is it paying when a non-paying combination is on the payline, or is it just paying the wrong amounts for valid winning spins?
win detecting is done by the wipers on the reel arms. If the wiper contacts are not on the correct rivets, you'll have problems.
the basic idea is the slots in the metal index discs position the wiper contacts on a specific colum of rivets on the contact plates. The w-1041-xxx document has details, but on the 809-B the following should be true:
1] the deepest index disc slots on all three reels correspond to triple bar symbols
2] the slot depth on reels 1-2 for a triple bar is 7, so the wipers should be on the third column of rivets from the front edge of the contact plate (post pic if not sure)
3] the slot depth for the triple bar on reel 3 is 6, so when reel 3 is indexed in the deepest slot, the wipers should be on the 4th column of rivets
note the paper tapes can be repositioned by loosening the crimps and spinning the tapes in the tins. If someone took the index discs off the reel tins, it's possible they remounted them incorrectly so the tapes are mispositioned. The index disc and wiper position is what matters ... the reel strips are decoration that just needs to be positioned properly. See
https://bingo.cdyn.com/slots/bally_info/reel_strip_positioning/