Hi Pinsiders
a friend of mine had a "sometimes" fault in his Big Indian --- sometimes at start up - sometimes when changing to next Player / next Ball: 500 Points and a bonus given - sometimes two times 500 Points plus Bonus. I am glad I could fix the fault - but still it is mysterious - ifever You encounter this fault: I finally put a stripe of paper through all 5 switches "Drop-Down-Target when hit, plunge rewards 500 Points and a Bonus" - the fault never showed up with the stripe of paper making these switches electrically open for ever, for sure. I then adjusted these switches a bit more open (gap) - fault never showed up again (we have played about 15 Two-Player Games).

I used a 24Volt-Testlight hooked-up parallel to a coil - first Coil-100-Point-Relay (Yes, the fault comes through this Relay) - second hooked on Coil-500-Points-plus-Bonus-Relay (Yes, the fault comes through this Relay) then I manually activated the O-Ball-Return-Relay, P-Add-Player-Unit-Relay, U-Control-Bank-Reset-Relay (strange - fault not with P-Relay, hmm - but the O-Relay activates the Ball-Return-Coil - this is a bit like an earthquake running through the playfield - eventually actuating one of the switches worth "500 Points plus Bonus" - very strange maybe the U-Relay then actuating the Control-Bank-RESET-Coil (on the bottom in the cabinet) also sends an earthquake through the whole pin ...
My friend then said "hammering with the fist onto the playfield also, sometimes gives 500 Points plus Bonus - so I finally put a stripe of paper through all 5 switches (see written above).
Solved - but it is a mystery to me. Greetings Rolf