Yes, they are jumpers. They use them instead of jumpers when assembling the board because automated equipment can insert a 0 ohm resistor but not a jumper.

Internally failed open. Could be any number of things.

It looks like it's used to absorb voltage spikes from the solenoids and redirect them back to the HV rails through the diodes.

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W1, W3 & W5 should be jumpered for +25v & +50v coil operation. They should not read open. If W1 & W3 are open, replace with a wire jumper.

I am guessing your 0 ohm resistors may have just cracked, and your problem behavior is due to not having a spikeback dump available to it. These would not likely blow open like a fuse unless they were really cooked, in which case you'd have a lot of other board issues, blown diodes & transistors on aux board, etc. But please take this info with a grain of salt and make sure you probe and test components on those +25v & +50v lines. I don't want to be the guy that gave you the go ahead to blow up your game.