This repository includes a repro for a problem with Electron (or possibly Chromium itself) where when a transparent window is used with semi-transparent elements on the page, shadows and ghosts might linger even after the elements have been changed or removed.
It is a cool effect for simulating a crappy OLED, but in most cases undesirable.
The only fix I was able to come up with is a full window refresh.
Run using bun install to install Electron followed by bunx electron ..
Turns out this was a dupe of an old issue:
The "fix" is to add hasShadow: false when constructing the window.
This is a Chromium issue, not an Electron issue per se.
Other issues: electron/electron#8557 and electron/electron#3836.
According to the oldest issue, this is probably an underlying Chromium issue at its core.