Atari STe black screen with diagonal moving lines/stripes

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Hello fellow atarians!

I have a problem with my atari STe. As the title says when I turn it on it gets a weird screen like so:

Here are the specs and what I've done so far:

- Atari 1040STe, 4mb memory, hxc floppy emulator

- Strange rev board:

- No visual damage to the board/components

- 4 mb memory upgrade (tried multiple different simm's in different combinations and tried these on a other ste & worked)

- Replaced shifter chip (facebook ste group came up with that one, didn't work unfortunatly)

- Pushed all the chips in their sockets

- Also tried working floppy drive with floppies.

- Hold the reset button for 10 seconds when turning on.

- Video: 13pin din to composite cable

- Video: RF via TV

- Video: 13pin din to scart

- All gave the same result, see this short video: https://vid.me/e/UxCW

- Pressing keys on the keyboard give the typical beep sound so sound works I guess?

- Hxc floppy emulator works great on other atari's, on this one it doesn't seem to load much. See this short video (beep = st cold reset): https://vid.me/e/dojE

- Tried a different, known working, PSU still same result.

- TOS roms are soldered (so no socket's damnit, I have 2.06 roms laying here though but too scared to solder and fecking the board up)

Even after all that, I can't figure out what's wrong.

I have ordered a HI-res din to vga cable to test out if the ste is maybe stuck in HI-res mode or something. (read it somewhere, can't remember).

Warning, I don't have much hardware knowledge (so pls not too much jargon) and I don't have precise soldering skills and money ( )

Is there anyone here who might have any idea what it might be?