A customer reported an issue to me, regarding the modification of an existing error with their items in ESE version 256 Service pack 2. He could open up the item and then immediately save the item, but the error would display.
He had the Sales Unit field hidden and it required a mandatory value. After he unhid the field and added a value from the search, everything worked fine. He did not have this issue with previous versions of Synergy Enterprise.
Be aware of this possible issue.