Writer text boxes disconnected from text on subsequent edits

I have created some text boxes with text in them. However, when I go to edit the text later:-

a) the box and text are separate in that the box can move without the text
b) the text box doesn’t expand when additional text is added

What am I doing wrong please?

Many thanks,

Allan

Which operating system and LibreOffice version do you use?

Does this happen only after save and reopen?

If so, are you saving to a Microsoft file format (rtf is the likely culprit)?

Windows 10 and Version: 6.3.3.2 (x64)

Yes, I am saving to Docx.