Word Document only opens correctly in Safe Mode

Hi, I have search the forum but I have been unable to find an answer.

The document I have been working on has stopped responding, it is a couple of months work with plenty of track changes.

I can open and use the document in Safe Mode, however if I save the document and try to reopen in normal Word, the document says 'not responding'.

I have run the Office Repair tool, I have checked for incompatible 'add-ins', but it is still the same.

Can anyone suggest anything else.

Thank you