Text Stops Filling Text Box in InDesign, Leaving Large Empty Space

Suddenly the text stops filling a text box; a large part of the box remains empty, no matter what I do.

The work around is to fit to text and flow to a new text box which I've put in place, but this may cause extra problems if the preceding text has to reflow. There is no page break I can find (and I deleted them all when I brought the text in from Word).

I am making corrections to this complex document, and this problem just started occurring.

I am attaching a screen capture and the original document. The problem is on page 30 (and others).

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