BK2K is System 11B. The flippers are not transistor driven but directly driven by the flipper cabinet switch closing.

The schematic shows Q67 energizes the relay that enables the path to ground for the 4PDT relay (enabling the flippers).

I think darcangeloel has a very good suggestion. If the lower right flipper works but the upper right flipper has problems the power to and ground from the flipper goes through an interconnect board at the back of the lower playfield. Check the connectors and pins on that board. Possibly a cold or cracked joint on it.

There's an interconnect board at the back of the lower playfield that allows the entire upper playfield to be disconnected and removed from the cabinet. It's not the interconnect board in the back box. It's a smaller board that funnels all the wires from the lower playfield to the upper playfield.

bk2k_upper_playfield_interconnect_board (resized).jpg

I'm not sure. You're asking for suggestions. Here's the thought process / logic.

You've said that the lower right flipper functions correctly but the upper right flipper does not. This would suggest that the problem is between the lower right and upper right flipper. The power for the upper right flipper comes from the lower right flipper but only when the stacked (ganged) switch closes (the EOS opens and closes the stacked switch). The power wire goes to the upper playfield through the interconnect board at the back of the lower playfield. Return from the flipper comes back out through the same board.

I don't know how continuity measures through crack/cold joints. When I spot them I usually fix them.

It can't hurt to check the board.