Mail Merge - Word primary, Excel secondary - track changes marking

[voyagerone]

Using a 'Word' document for mail merge letter. Using a database in Excel.
The mail merge process is simple enough. Before sending out a few hundred mail merge emails, I always like to send one to myself to check that all is ok. Lucky I did. I have a few email addresses.
The document received is completely wrong with lines crossed out and with words replacing other words. Some text is in red. I thought it was a mark up problem so I cancelled all the markup settings and stated 'No markup', but still the same.


I don't know where to look to solve the problem. It must be a problem with a setting somewhere. See screenshot.
Any assistance is appreciated.
Cheers,
L.