Looks like there's a loose resistor in pic 5, at R44.

I have seen this as well. It seems to be by design and is actually two resistors soldered in series. They seem to be attached quite well after double-checking them.

Check your RAM chips for solder cracks.

that issue is either bad ram chip or a bad connection somewhere. its honestly a coin flip telling which one.

1: you can re-flow the solder joints, careful to not short anything. this happens to be a cheap & easy potential fix.
2: replace the ram chips. They are very standard chips and should be easy to source replacements.

It looks like it could be a problem with the address lines rather than the data lines, since it looks like some of the pixels are repeated rather than just being corrupted (random colours/static). You could try pressing on the chips with the card on and the corrupted screen, and you might notice the flickering stopping or starting again when you press on one of the chips (don't expect the screen to clear up immediately though, the data in the RAM has been written incorrectly by this point.) I've done this before to help narrow down where a bad connection was. But if it is a bad RAM chip as @luckybob says, this probably won't do much.

Also give the chips a good clean, making sure there's no dust or gunk in between the pins. A clean paint brush is really good for this. I've had metallic dust connect two address lines before that causes a similar sort of visual effect, and a good clean was all I needed to fix that up.

Fixed! Thank you for all your suggestions!

Turns out there was indeed a memory pin on the top memory chip that had gone cold. Re-flowed it, messed with the jumper settings again and we have a winner! I'm very happy as this card out-performs my 5429 by over 10% on most benches.

Thanks again 😀 😀

That's great, glad to hear you got it fixed!