There were and are probably still thousands of people using RGB SCART with early model Xboxes ie. non-Xcalibur. I have two Xboxes connected by RGB SCART to two different CRT TVs a 32" WS and a 20" 4:3. One is that LE Green v.1.2 I mentioned, the other is my oldest XBox a v.1.1.
The RGB SCART cables I use are nothing special, one bought from Amazon <£5 ($7) the other from a high street store for similar cost. No banding or other such problem with these TVs.
If there had been some inherent trouble caused by the video encoders everyone would surely have had suffered the same thing and, rightly, complained. The fact is the vast majority didn't. Therefore whatever the problem is it is likely something more complex or more specific to your set up.
You've not said why you're using RGB SCART instead of Component - is there a reason?