Nanao MS-2931 vertical wobble

[GroggyExpulsion]

I'm not sure if this is a groovymame issue, but i've recently had this come back from a service and it was given the thumbs up and have no other way to check this. 

I'm using the groovyarcade MS-2931 monitor profile and occasionally experience wobbly vertical lines, sometimes they are quite exaggerated and other times similiar to the below video

https://www.youtube.com/shorts/a885N61Zzz8

[Calamity]

Try adjusting the h-phase / h-shift potentiometers and see if it has an effect on the problem, they might be dirty or faulty.