Reply To: copy/paste issue of text frames (with copy) from one file to another

I have seen this. This can happen for a number of reasons, including:
https://creativepro.com/beware-basic-styles.php

But sometimes it’s very mysterious. Try clicking inside the frame in the original document and doing something to cause text reflow (see https://creativepro.com/force-text-reflow-when-indesign-forgets-to-flow-the-text.php). Sometimes your old document is stuck in an old reflow state and doing this makes it reflow to the newest algorithm (which may or may not be what you want).