Quite a rare issue. I was about to block [[User:The truth loader]] for vandalism and already had the report user form open for this. After checking their edits and pressing "Block User" huggle displayed a message box stating the user was already blocked (Thats good).
After closing the message box however, the below "Your blocked" template was still placed, even though the user was not actually blocked by me:
Version: 3.0.0
Severity: critical