Issue with cmd-z in normal text edit to paragraph

I don’t know if this happens to anyone else, but using Cmd-Z in normal editing mode and when editing a paragraph box, if i use cmd-z to undo an entry, the text box i’m working in is suddenly converted in to an un-editable Div.

Saving and re-starting doesn’t fix it .

My only solution now seems to be to create a new text box / paragraph and copy the content in from a preview browser before deleting the now useless element.