Word document overview : bug in table of contents and problems with Word online

Sometimes in some documents, there is a bug using the links inside the table of contents : 

• first click is ok, document scrolls and then it is possible co come back to the table of contents...
• and then no more click is possible in the table of contents

I tried to update the table of contents in Word, ans saving again the document, same problem.

More over, viewing the document is different between : 

• overview
• word online with read only access rights
• word online with collaborate access rights

Any clue? :-)