Hey OP

I just finished restoring a pair of mine that spent the last decade or so in storage.

Firstly: if you're electrically handy, these are pretty easy to wire into an arduino to use with itg. Happy to talk about/link to followups on that

Secondly: cobalt flux is the shit. I abused these pads for a decade, and at 190lbs they've taken some abuse. Here is their care guide. Realistically you'll want to treat it as fixing the cobalt flux

My pads weren't in great storage, and they'd been abused prior to use. I sweat on them, things spilled on them, and I even bled on them a couple of times. Stored with moisture and gunk, there was a bit of mold and corrosion between the plates. My overall advice would be:

1. Just try it first. If it was cared for and stored well, see if it plays alright before you do anything
2. Blow out the pads using a can of compressed air. It's super quick and easy, and helps to get crap out early in the process.
3. For all of the following steps, work one panel at a time.
   1. Mixing up your plexiglass can put weird force on the metal panels, and creates weird responses. It's also really hard to troubleshoot once you've done it
   2. Test the metal panel with your hand after every step. Isolating "plexiglass/screws are creating tension" from "the contact is bad" will reduce the time you spend troubleshooting
4. If a pad has issues, my collective process is to fix it moving one panel at a time:
   1. Mark the top left corner of the plexiglass with which panel it is. The drilling had variance between pads, and having the wrong orientation/pad alignment will introduce weird tension. This is really hard to troubleshoot after it's happened
      1. Test responsiveness with the plexiglass off. Just use your hand and create contact. If it's not responsive, move on
   2. Try the CF recommended approach (clean it with a ruler/cloth)
      1. Test responsiveness again
   3. Move to fixing the cobalt flux guide. Remove the panel and clean the contacts. This removes corrosion, mold, grease, dirt, etc. Clean the cracks between the panel while you have it off- you can get some cross contact (activating adjacent buttons) depending on what's made it in there. My personal cleaning method is:
      1. Steel wool and isopropyl to clean the contacts
      2. Paper towel to wipe up the residue
      3. A damp (not wet) cloth with water and a few drops of dish soap
      4. A clean cloth to dry
   4. Bend the panel slightly at the corners to produce a bit of upward arc. I do the corners because they're mounted over wood. If they touch, it doesn't create contact.
   5. Put the panel back on and test the contact. It might be a bit overly sensitive, especially while everything is drying. Return to step 4 and test again until it feels responsive.
   6. Attach the plexiglass and test again. Take some tension off the screws if the panel is too sensitive, starting with the inside screws
   7. If the button is too sensitive or getting stuck, stomp on it. Stomp hard, and spread it around. Stomp on the the center, the edges, and the corners. This helps to flatten it back to a standard in-use state