Unknown Error - Status: One of the updates to a closed ticket was rejected

Hi, 

I have been using the beta quite a bit over hte last couple of days to correct a missing tag on some tickets. I am primarily using the API to make these modifications. 

I have spotted an issue that occurs occasionally both via the API and the UI. When adding one or more tags, I sometimes get the error:

{"error": "RecordInvalid", "description": "Record validation errors", "details": {"status": [{"description": "Status: One of the updates to a closed ticket was rejected"}]}}

In the UI it appears as follows:

I don't see a reason on the tickets where this has occurred as to why they cannot be updated. It is also not clear when adding multiple tags which tag is problematic. I have seen this error occur when adding one tag as well, so it is not simply because of adding multiple tags. 

I would like to understand what could cause this error? 

Best regards, 
Stephen