Take a look at these two images of original SCELBI boards.

Backwards Capacitor

The second one has the plus sign manually removed and the capacitor reversed. I did a quick test in my “lab” and found that indeed the “negative” side is about 1 volt higher in value than the “plus” side. Those capactors definitely should be reversed. While you are at it, make it authentic and manually remove the “plus” sign.