[Typo3] In tt_news: firstImageIsPreview doesn't work

[J. Michael Adams]

When I created my tt_news pages, I checked the box that says the image will
appear only in the teaser, not in the single view.

I think it worked at first (I don't remember for sure), but now it doesn't
work - the images always appear in the single view.

I've checked all my typoscript and can't find any place that
firstImageIsPreview is cleared. I made sure it was checked in both the
summary page and the single view.

Does anyone know how this flag can turn off? I mean other than the obvious
ways - on the extension setup page and in typoscript.

Thank you,
Michael