my paperwork says the 918 is the basic mustang, while the 918-1 is mustang with diverter (mechanism on door to direct coin to overflow instead of hopper when the hopper is full).
the paperwork for the 918-1 is on
https://bingo.cdyn.com/slots/assuming your machine is the same as the paperwork, the switch stack by the hopper motor is the hopper cam switches:
switch #1 (bottom switch) - schem G2 - white wire 50 and green wire 40 on the blades. 120V circuit for hopper motor control to make sure the motor stays on until the hopper cam switches are open. If it doesn't work, it's probably not a big deal. May result in a coin payout being off +/- a coin - depends on the timing of a coin roller switches, the payout counter stepping up and the payout relay unpowering.
switch #2 - schem F9 - blue/yellow wire 23 and grey/black wire 98 on the blades - replay register step-up coil circuit
can't see on your pic the complete wiring of the hopper cam switches, but obviously it's not right currently.
the other cut wire is white/blue? If yes, is it going to a switch on the payout relay? If yes, it's probably wire 52-1 (schem F12) and the cut end should be attached to the hopper switches that get operated when a coin goes under the roller. Looks like it's a circuit that allowed cashing out credits - making the hopper eject coins and decrementing the replay register until the register was zeroed.
you'll probably want to remove the top bolt from the payout counter frame, loosen the bottom bolt and flip down the payout counter so you can see the ratchet/gear side to see where the wire could go.
post as many pics as you like, and if bored email the highest possible resolution pictures to slotpics@cdyn.com and I'll add them to the above site. A pic of the entire front of the game and as many internal pics as you have patience for is helpful, as well as a pic of the lamp side of the top insert when the glass is removed.