Well, the problem has re-asserted itself again. It seems much more subtle now however. Barely noticeable. Instead of the screen dimming for a second or two, if you blink you miss it. The severity of it is greatly decreased as well. I think there may be some small screen deformation, when I look extremely closely. Maybe a pixels worth. And a miniscule amount of blurring as well.

I'm noticing some coil whine I didn't hear before. Especially at certain resolutions. Also when I turn down the contrast. Not sure what that's about.

Namrok wrote on 2022-11-26, 01:40:

It seems much more subtle now however. [...] And a miniscule amount of blurring as well.

It's worth a try to twiggle the focus pot like you did with the screen pot. If the primary issue really was a bad contact in the screen pot, you might have a similar issue in the focus pot, too. The blurring you observe supports the theory, that the focus voltage might be unstable.

Namrok wrote on 2022-11-26, 01:40:

I'm noticing some coil whine I didn't hear before. Especially at certain resolutions. Also when I turn down the contrast. Not sure what that's about.

Coil whine at certain resolutions can be normal. If the contrast influences the sound, the source of the whine is likely not the deflection circuit, but the B+ regulation circuit that generates the primary operation voltage for the deflection/high voltage generation circuit. In TVs and fixed-frequency monitors, the B+ voltage is constant and directly generated by the power supply. In multi-sync monitors, you usually have a switch-mode regulator to generate a scan-frequency dependent voltage. The load on this regulator depends on overall picture brightness. Coil whine is a typical symptom of old age of a switch-mode regulator, because some coil windings can become lose over time, but might also point to worn electrolytic capacitors around that regulator.