The attached test application can be used to reproduce the issue:

The Testprogram consists of a area with a QGraphicsTextItem and buttons. When you doubleclick on that area the text could be edited. At the bottom of the test widget are some buttons to interact with the text/make settings to the document.

• the html-button sets the documents html-string to itself and make a debug message
• the make changes button changes the document so that the error happens
• The example-button just sets a predefined html-text with a <table>-tag