Definitely not a flyback issue.
Btw, in the other thread you posted RGB pictures that look fine.
Are all the pictures 50Hz or 60Hz, or are they mixed?
Its not clear from the description, since later on you write that PAL (50Hz) looks fine on composite.
As spaceman88 suggested, get a freeze spray, let the monitor warm up and start exploring.
I'd start with the PSU, then move to the HV section.
Thanks for your reply. The monitor works without issues with a PAL (50Hz) Amiga A1200. I had tried RGB, and composite and the monitor works without issues.
But any NTSC source which I had tried with my other Amiga A1200 (that is NTSC) RGB and composite the monitor gets the distortion (starting from the TOP bending to the left) and getting worse the more time the monitor stays on.
Other NTSC sources I had tried with the same Results; Turbografx, Supergrafx, PC Engine, PSX, Sega Genesis.