Tagging shared documents

Hi there,

I don't know if this is a bug or a feature of the way that shared documents work.

I've added tags to my own documents, that's all great and works fine.

I also have a document shared to me personally, and I've added a tag to that which also works fine.

But I have another document, that's been shared to me as part of a group, and it seems that I'm not able to tag that. The tag entry box appears as normal, but when I enter a tag and click the "add" button, nothing happens.

Is this deliberate, or a peculiar bug with my document?

best wishes,

Mo