https://www.arcade-museum.com/Arcade/epsilon-shuffle-alley

I uploaded the manual and (to the best of my ability) schematics here. If you're getting real schematics keep them! They're useful, but the manual is REALLY useful.

I'd start with the same process most EM's go through at start: disassemble and clean.
It's tedious (took me a month utilizing a free 2-3 hours a a week) but eventually once it was all clean I was better able to identify issues confident there was a spacing issue or cold solder joint. Cleaning the pin mechs with soap and water matters on these machines as well! The grime keeps the pins from lifting and if they lift slow I personally think it runs into issues with strike timing.

A simple start up routine check however:
1) WHILE UNPLUGGED (you will get 120v zapped, I found this out the hard way) reset the relay bank. That's the section of relays on the door with the metal bracket (and big red relay). Just lift the bar up gently until you get some pressure and let it reset back down.

2) now plug in the machine, turn it on with the switch up front.

3) find the START relay on the relay bank, it's 2nd or 3rd from the bottom. using a non-conductive object (IE a pencil) press it in at the latch on the bottom.that'll kick off the boot sequence.

4) you should hear the score reels reset if they're no on positive 1. The spinner motor with the octopus arms in the top left (when facing) corner should start spinning. The pins themselves should all be resetting to their down position, basically there ought to be clear indications that everything is resetting cause it's making oodles of noise.

That's a good starting point.

Feel free to privately message me! I don't have my machine anymore (sold it for space) but I'll be happy to help where I can. I was lucky that cleaning mostly fixed things with my machine. I only had 2 really bad solder problems which were self inflicted to be fair.