reapplying Parent page to document pages with existing text and getting odd results

I’m resurrecting an old QuarkXPress v. 3.31 document using InDesign 20.5.2 (2015 MacBook Pro Retina 15” under Monterey).

The original QXP had master pages (INDD calls them Parent pages I see).

There are various oddities in the import (e.g., all items on the document pages are shifted 2.75” to the right! weird.). Another issue is fonts. I have replaced several missing fonts using modern Adobe equivalents. This change affects, e.g., headers on the Parent pages. When I go to update the document pages assigned to those Parents, InDesign is inserting an empty text frame onto the doc page and “pushing” the existing text frame to the next page in the document.

I assume this is due to my misunderstanding of text flow on Parent pages. The Parents for the body of the doc indeed have a blank text frame laid out within the specified margins. (I see the option, on Parent pages’ text frames to “Click to make this story the parent’s primary text flow.” Which means very little to me.)

Should I just eliminate those text frames on the Parents in question, THEN reapply the Parents to the appropriate doc pages——just to update my headers that bear title, author, page #? Of course, I need to retain the existing chained flow of text among all the existing pages in the 300-page novel. Don’t want to mess that up.

I’m trying to avoid having to manually update all headers.

Thanks!