Hello,
I just got a non-SEGA RGB(Scart)(Non-official) cable for my two Euro PAL SEGA Mega Drives Model I (Bulky models)
I have a standard 4:3 display 21” Flat SONY 50/60HZ EURO PAL/NTSC TV with RCA-IN, RGB-IN(Scart) & RF-In (Antenna)

All my other consoles that are connected to this TV via the RGB-IN, work perfectly, at 4:3 display ratio. But when I connected both my Mega Drives (Model I) with this new cable, the display will switch from 4:3 to 16:9 after a few minutes in random.
My TV has a button that I can switch back to 4:3, but after a few minutes it will switch back to 16:9 again.

My TV doesn’t have a problem as all my other consoles (PS-1, PS-2, DC, Saturn, work perfectly at 4:3 via RGB(Scart) constantly and I don’t thing the problem is casued by my two MDs.

This specific RGB(Scart) cable only uses these pins: 2, 6, 7, 8, 11, 15, 16, 18, 20 (pin 2 is connected to pin 6, internally)
I’ve never had an official SEGA Mega Drive Model 1 cable so I wouldn’t know if these are the right connections, but what else could be causing the random switching from 4:3 to 16:9?

Thanks in advance.