I have a Beovision MX1000 to play with my Super Famicom. It is plugged via a SCART cable.

But every time I turn it on, the picture keeps scrolling vertically at varying speed. Sometime it seems to scroll horizontally as well.

The issue fixes itself after waiting for a while, but it can take up to 30 minutes sometimes which makes it very unconvenient to use.

I caught the issue in video if you want to see how it looks like: