Display Name in Content type and List

I seem to have an issue, which is strange but true.

I have a content type, and a particular field has its display name to say "XXX"

All other fields don't have the display name set in the content type.

Then I have a list that inherits from the content type, and the list has display names etc as u would expect.

Finally I have a page that uses the list instance.

I updated the field label's/Display names in the list only.

If I simply deploy the solution, all but the label which has its display name set in content type, deploys/works correctly.

If I reactivate this feature, all labels revert back to their original state.

What am I doing wrong.

I have tried to disable/enable the feature, redeploy the solution, as well as few other things, e.g. http://ift.tt/18AguGZ

Any ideas would be great.

Thanks