Reply To: Problem with text formatted with paragraph styles

It’s possible the Basic Style is defined differently in the two files. Reflow is also possible when copying from a very old InDesign doc to a new one. Or perhaps there is local formatting on the text (look for a + symbol next to the paragraph style in the para styles panel).

In general you do not want to copy and paste from Word to InDesign, except for very small amounts of text. You should use File > Place.