I’ve noticed that when a unique constraint error appears in an edit screen after a user clicks ‘OK’, the error continues to appear even if the data causing the unique constraint violation is corrected and a user clicks ‘OK’ a second time with a valid edit. However, if you close the edit screen and reopen it and make the same valid edit again, it is accepted. The unique constraint error seems to persist at the screen level until the screen is closed.
Сould you please provide more information about the problem: which version of the Platform do you use, what kind of a unique constraint is used in the project.
Also, it would be helpful if you provide a small demo project with a reproduction scenario that demonstrates the issue.