Could simply be that there is a column or page break character imported from a Word file or a paragraph style that has a Start on next page setting
Often caused by keep options in the paragraph styles.
Sometimes it can also happen for no reason -- just because the story
recomposer didn't kick in.
If that's the case, to recompose all stories: Shift+Enter to open Quick
Apply, and then typing "recompose" should bring up the required item:
"Recompose all stories." That can somtimes fill in white gaps at the
bottom of pages (fairly rare).
Bonus question: Does anybody know what the difference between "Recompose
all stories" and "Recompose all stories immediately" is (since they both
seem to work immediately!)?
Check the keep options on the empty paragraph above the anchored frame. I bet it' set to keep with previous and Keep with next (or the one with the anchored object is also set for Keep with previous).
That seems to have done it!! I've never heard of that. Fantastic. Thank you.
Thanks for the suggestion. I have checked that and found a few where that's fixed it but it hasn't done it every time. The "Recompose all stories" seems to have done the trick for the ones that just wouldn't flow.