Unwanted Tag when drag & drop

Whenever I drag and drop a document into a Devonthink Pro group a tag is always appended no matter what the document is. It is always the same tag and it was one that I created a ling time ago. This is rather annoying as I have to remember to delete the unwanted tag, if I forget (which I often do) I end up with loads of unwanted and irrelevant tags. I have tried removing all the tags form all documents and deleting the tag from the tag list, but it is still happening. Any ideas would be great on how to stop this happening. Many thanks.

Does the group have any tags? Or do you use any smart rules that add tags?

Not that I know of in either case, how do I check that please?

The tags of the group can be checked in the Info inspector, the smart rules in the sidebar.

I seem to have cured it! Thanks for your helpful suggestions.