I am at about page 92 of a 140 pager. Worked a bit in ID (not an expert but ok with the basics). The text frame on this page appears to be normal as is the text flow within the story overall. No gremlins (hidden characters). All normal in the story editor.
About 1/4 of the way down the page text frame, the copy flows to the next page (ie, it flows prematurely leaving a blank part on the bottom of the frame). I have reset plist files in Library, smart flow on and off, recompose (cmd-opt-/) multiple times, resized frame (bigger, smaller etc). It is like there is a hidden block of invisible deep space (the "squatter") stuck on this frame taking up 3/4 of the frame and allowing only 1/4 of the frame to be used. Adding pages before or after affirms the existence of this gremlin block that insists on squatting on this page's frame like crazy glue. All activity before and after this squatter page is normal. Text threads all normal. All paragraph styles are routine (body copy and basic headings). I don't even have anything like an image, anchors or ANYTHING. Just plain old text - I plan to add images once text content done. Adding and deleting text (and pretending to be a pianist with forced recompose yields me the proverbial deer-in-headlights-look from the invisible squatter. Latest Mac build Monterey 12.5.1 and latest download from Adobe for the latest and greatest of ID. No other programs loaded. Is this a bug or something else I have missed in the How-To world? I am stuck but prefer company besides the silent squatter. Text for the story originally loaded from Word (mind you, who knows if that has hidden whatever in it but I have reason to believe it is as clean as the Place permits). It is like the frame is convinced it is 1/4 (about) the prescribed size (Property panel all normal for Letter size frame less margin allowance). 2-UP spreads. New install (last couple of weeks) after being away from ID for a bit. It's been a tad unstable (crashes periodically but behaves after plist fix). Machine overall is stable and quite plain and not loaded down with a 1001 gizmos. Thanks! Suggestions greatly appreciated.
I would first go through View>Extras>Show Frame Edges. This will outline every frame on the page (even locked ones) and possibly reveal your "silent squatter". If you do see a hitherto unseen frame try going through Object>Unlock All On Spread and if anything unlocks then delete it. You might also try seeing if there are any hidden and/or locked objects on a layer or sublayer in the layers panel. Any objects that you do find sound like they have Text Wrap applied to them.
Another possibilty is that there is a "Move to Next Frame" marker somewhere in your text. Try going through Type>Show Hidden Characters and look for a small "v" shape at the point where the text disappears. If there is one there then delete it.
To add a bit to Bill's response, if the break comes at the end of a paragraph I suspect you (or the original author if that's not you and you are importing the text) hit the enter key on the number pad at the end of the paragraph instead of the Enter/Return key on the alpha keyboard.
The one on the numpad is, by default, a column break shortcut, which in the case of single column frames pushes the text to the next frame. Occasionally I've run across computers with weird keyboard mapping where toggling the NumLock setting will switch the behavior of the numpad Enter key, but this is pretty rare and can be addressed by creating a custom keyboard shortcut set.