Visio Tags automatically updating

[DrSimon]

Resubmission to correct forum.
Some advice please. I am updating some corporate Visio documents and somehow the contents of the Tags property is getting updated to its original contents if I delete it and save. Oddly enough, if I try to replace with a new tag, that appears in before the 'old' data once saved and I can then delete the new tag data, but the original remains.
I can't find any associated VBA code or Add-Ins. Does anyone have any idea where this data could be coming from and how to control it?

 

[DrSimon]

A colleague has pointed out to me that they are actually the labels of the swim-lanes in the diagram. So this appears to be a 'feature' of Visio. I've tried to search for this but can't find any reference to it. Does anyone know if it can be turned off?
Thanks
Simon