'Do Not Reassign Owner' checkbox gets unchecked

Root Cause

This is working as designed. The 'Do Not Reassign Owner' checkbox requires that no specific user or queue is selected in the 'Assign to' field before it can be checked. If a user or queue name is already populated, the checkbox will not persist.

Steps to Configure 'Do Not Reassign Owner' Correctly

1. Navigate to Setup | Lead Assignment Rules(or Case Assignment Rules) and open the relevant rule.
2. In the rule entry, remove any existing user or queue name from the 'Assign to' field.
3. Once the 'Assign to' field is cleared, select the 'Do Not Reassign Owner' checkbox.
4. The checkbox will appear grayed out and the 'Assign to' field will display 'Same User'.
5. Click Save.