FWIW, something like that happened to a user in my organization. It seemed to be a temporary glitch that went away on its own after she navigated to a different tab in Qualtrics and returned to the report later.
Hopefully that's the case for you, and I also hope this is looked into by Qualtrics. The interface in Reports is regularly unstable, both when I'm making a large number of edits in a session, as well as when I return to a report I created previously. To the latter point, just this morning it appeared that some text fields in my report had lost their copy in a series of reports. They curiously returned on their own after a couple minutes, but not before causing an unwanted morning panic.

Thanks Matthew,
Unfortunately, since when I posted this question and now, nothing changed on that table. Alternate row colors is still flagged, but still no colors. Also not in the public report. :(
I do share the frustration with report editing. I also regularly have the impression that it's not stable (or I am editing too fast?). Especially when copy-pasting a set of graphics, when I have some similar questions and want a page for each question with the same graphics. With a drag-select-box I select my 6 graphics, copy, position my cursor at the palce where I want to paste (new blank page), then paste, but they are pasted very randomly scrambled across the page...

That's disappointing it's not resolving itself. I really like a lot of the advanced features in Reports but the bugs in the interface make it really time-consuming and extremely frustrating to work with. I have trouble just dragging or copying one object at a time; I wouldn't even think of trying six! Also, page breaks disappear at random, objects that I drag within the middle of my report end up automatically at the beginning, colors in my graphs change at will, and now the same text that momentarily disappeared earlier this morning has vanished AGAIN, replaced by "Double click to edit". Not to turn this into a venting session, but if anyone with Qualtrics is listening, it gets tiresome to have to convince colleagues that I share the public reports with that Qualtrics sometimes has a mind of its own and will change charts in a live report even after I double and triple-proof them!