When an user creates an override of the below UI action on TOP/ACME domain, below are the things observed.
1. The new UI action is in TOP/ACME domain and it is overriding the global UI action (verified the override field). Still when the user sees the global domain UI action
2. If they inactivate the global domain UI action, then the TOP/ACME UI action is seen.

Global UI Action: https://<instance name>.service-now.com/nav_to.do?uri=sys_ui_action.do?sys_id=sysverb_post_update

1. Create a UI action overriding the below UI action in ACME domain. Make sure you check the override field. Give the name as Update-ACME
https://<instance>.service-now.com/nav_to.do?uri=sys_ui_action.do?sys_id=sysverb_post_update

2. Change domain to TOP/ACME

3. Go to ast_contract table. If not present, add the 'Short Description' column to the list

4. Select 2 records from the left checkboxes

5. From the list context menu, select the 'Update Selected'

6. In the new form, update something on the short description field

7.Notice the Update button is showing the global , not the Update-ACME

8. Click Update. Notice the update will be done.

9. Inactivate the global UI action

10. Do step 4-6

11. Notice Update-ACME is shown.

12 Clicking it won't do anything

After carefully considering the severity and frequency of this problem, and risk of attempting a fix, it has been decided to not address this issue in any current or future releases. We do not make these decisions lightly, and we apologise for any inconvenience.