Problem: Text frames suddenly become empty
When working on a +400 pages book, and when I'm in the middle of simple text editing (most of the time; any editing that causes an increase or decrease in lines), suddenly one text frame (other than the one I'm working on) become empty, and all text will move to the next text frame. To solve it I have to edit some text; like adding a paragraph then deleting it. And another fix is by resizing the text frame!!
My version is 2020 last update. Book is in Arabic.
Cannot understand why that is randomly happening!