[BVM-A14] Interference while moving mouse

[Alf]

I have a BVM-A14 with a clone BKM-68X card, connected to my PC via a VGA cable.
The PC has an RTX 4070 and I've tried an Icybox HDMI>VGA adapter as well as a no brand DP>VGA adapter.

So I extend my desktop and put 480p since this BVM is multiformat. Works flawlessly. Switching to 720p works as well but comes with a strange anomaly. When I move the mouse cursor to the right side of the screen, I get interference like this;


The interference follows the cursor and disappears when the cursor goes back to the left side of the screen.
Any ideas?

[Josh128]

Thats an interesting one. Try this test-- type "Change mouse pointer size" in the Windows search box and make the pointer as large as possible. Then move it around and try-- does the distortion get worse? It could be related to the intensity needed to create the white color somehow affecting the deflection circuitry.

What happens if you drag a white window around (of varying sizes)?

[Alf]

It looks like it's not the mouse or the colour white.
When I take any object and move it to the forbidden zone, the image breaks down.




Someone told me to install custom modelines. How the heck do you do that?

edit
Ok, I'm now 90% sure it's the DP-VGA adapter's fault.