Shakey screen on G7400

[Relo]

Hey, I just finished RGB modding my G7400. I also had/have this on the RF connection. I initially thought because of it being hard to tune right I assumed it was something with interference, but seeing as I also get it with RGB I doubt it.

How can I fix this?

Photo's of the screen: https://imgur.com/a/DoFb3ep

[Relo]

Bit of an update.

I left the machine on for roughly a minute or 2 and the image began to stabilize. Though it didn't register any inputs it seemed. (Fixed)

So after a reboot I got this:

(or sometimes a black screen)

Audio seems to work fine as I get a nice bootup sound. Though it doesn't seem to react to any input anymore.

[grips03]

1) Confirm what type of sync you display needs.
2) Double check the sync line from console to display.

[Relo]

1) Confirm what type of sync you display needs.
2) Double check the sync line from console to display.

1) I get get the same image over RF. Though issues with sync wouldn't explain it going from a shakey screen to outright gibberish and the keys going unresponsive as far as I know.
2) There is continuity on sync.

Update:

Apparently I didn't put my keyboard cable in well enough and got loose. Which explains it not taking input. Now it does.

[Relo]

Sadly still have the issue.

After reading this: http://videopac.nl/forum/index.php?topic=1592.0 it might actually be a sync issue (but not the connection to the RGB connector, as RF has the same issue). Though reading that thread I have little understanding how to actually try that fix... Though it also looks like this before it went really bad: http://videopac.nl/forum/index.php?topic=3203.0

Does anyone know what I can do to fix it? I feel like I'm at a dead end.

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Edit:
Tried quest for the rings (Dutch version) as an easy reference. Maybe someone can see better now what the issue is?
https://imgur.com/gallery/J3yj7rv