Williams/Bally Rubber Bumper Plug/Grommet
http://www.pinballlife.com/index.php?p=product&id=276

This is a diode on the switch matrix. It isn't common for them to fail, except where they experience high vibrations--something the flipper assembly will provide. I would just replace the diode with a new one. Any 1N400x (where x is 1, 4 or 7, so 1N4004) will work there. Make sure the band is in the same direction.

If it's not the diode, look for a bad connector, or possibly broken resistor capacitor array next to the connector on the Sys11 main board (I fought with that issue on my F14 that was causing phantom tilts---I posted pictures of the problem and repair in another thread).

You definitely want to get the EOS switch working. If it isn't sensing it (always off), then you will run the risk of burning out the coil, melting the sleeve/increasing binding in the flipper assembly or shorting out a driving transistor on the CPU if you hold the coil on (like to stop the ball at the base of the flipper bat). If it always is sensing it (always on) then you will never have enough strength in the flipper to hit a ball as only the holding coil is working not the main driving coil.

If you have a multi-meter you can test it to be sure, but since they cost around 5 cents each, easier to just replace it to be sure. Not sure where you picked up that it is a capacitor from the manual? Were you looking at the 2.2uf bright yellow rectangle capacitor that is secured to the side of the leaf holder that goes across the high voltage inner switch to reduce the pitting it gets from the high amp discharge on each flip? -- Yours does not look like it uses the newer coils/assemblies that require the capacitor. I think some F14's did upgrade to them while older ones didn't use them due to different coils.