S-Video input video artifacts

[eXtremeDevil]

Hi, I'm trying to capture a VHS. I have an August VGB100 Video Capture device:

https://www.amazon.co.uk/august-capt.../dp/B008F0SARC

It has two inputs, composite and S-Video. I understand S-Video offers a higher quality, so I'm trying to use that one to capture. However, compared to composite input, I see some weird artifacts on the video:

Composite:


S-Video:


Sorry about frames not being the same, but I couldn't pause the VHS. But I see the effect is clearly visible. The composite signal may have lower quality, but at least it seems somewhat clean.

I have tried with different S-Video cables and also with another capture device, a Hauppauge USB-Live 2, and the results are the same.

However, I have also tried the same cables and the same capture devices with a Sony Hi8 HandyCam and the effect is less visible with the August device, and nonexistent with the Hauppauge device.

So now I suspect of two things: the VHS player itself, or the SCART to S-Video/Composite device I use, something like this:


Where do you think the problem could be? Am I in the right direction? What is the origin of this effect?

Thanks in advance!