Ikari Warriors rolling screen on arcade monitor

[keropi]

Hiya!

I decided to try Ikari Warriors (JAMMA) on my GM0.171/6450 setup but the screen was rolling. I am using a Hantarex POLO 25" 15Khz arcade monitor and adjusting the SYNC pot on it's controls did not help.
Is there a way to fix this? Should I make some kind of adjustment on ArcadeOSD to fix this resolution? I don't want to mess things up since everything else seems to run just fine.
The game uses the 288x216 resolution.

TIA for any info/help! 

[keropi]

found out that Puckman behaves the same, rolling screen.... I am using a J-PAC jumpered at 15khz if that makes an difference

[keropi]

well, no wonder this question had no answers... I had to tweak the V.FREQ potentiometer at the monitor chassis, this fixed the rolling screen in the affected games and did not break the other resolutions and/or console resolutions.
So maybe this helps someone in the future wondering why 95% of games are OK but a 5% have a rolling screen