Dreamcast vga 15khz shaking

I just made a vga box using the schematic on this page:

http://www.dcemu.co.uk/vbulletin/showthread.php?t=5694

with a toggle switch for 15 and 31khz modes. 31khz works fine but in 15khz I get some picture shaking on my arcade monitor.

Any ideas as to what might be the cause?

On the H and V Sync I would have put pots instead of rsistors to fine tune things like that.

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I'd recomend using the composite sync and not combing the other two syncs....

My Arcade montior requires that i clean the composite singal by way of an Lm1441