Zoomin mode is a bit finicky. Just a few days ago, there was a report of a problem when using zoomin with some added styles for “centering” the story column. After some investigation, I found a workaround that involves overriding a few very old zoomin-related styles that are defined in the “Vanilla” shadow stylesheet.
It’s possible that these same changes might fix this current problem as well.
See Centering the River - #9 by EricShulman for details.
Let me know how it goes…
enjoy,
-e