Linearity issues on 1353md only with Suikoden?

[cave hermit]

Trying to play Suikoden on my 1353md PVM, but there's this really distracting effect where the image seems to stretch as it scrolls near the top or bottom of the screen, which I can only assume is a linearity issue. Thing is I only seem to notice the scrolling distortion in Suikoden, and haven't really noticed it in other games or in the 240p test suite with the grid scroll test. I have also tried tinkering with the service menu and trying various v linearity settings, but it doesn't really help or makes the distortion worse. Does anyone have any idea what might be going on?