Additional assignment info edit with error Another row exists with the same value entered FND-2906?

Summary

Additional assignment info edit with error Another row exists with the same value entered FND-2906?

Content

Hello ,

When navigating into change assignment - additional assignment info of an employee ,and trying to change the first field of the additional assignment ,the type I marked in the screenshots - press submit - we get the following error :
'Another row exists with the same value entered for שיטת דיווח נוכחות. Enter a unique value. (FND-2906)'

added screenshots of the setup - the field we are trying to change is 1) unique key 2) multi row

How can we be able to correct /edit the existing additional assignment record without having this error ?