Notifications toggle preferences are not saved for a subwiki user

STEPS TO REPRODUCE

1. Login as Admin
2. Create a subwiki
3. Go to the new subwiki and create a user (e.g. U1)
4. Login with U1
5. Go to Notifications > Settings
6. Set the Pages notification toggles to ON (both menu and email)
7. Refresh the page (CTRL + F5)

EXPECTED RESULTS

After the page is refreshed, the user notification preferences are saved (i.e. both toggles are ON, as previously set).

ACTUAL RESULTS

Although the 'Saved!' message is displayed when both Pages notification toggle are set to ON, only the first setting is really saved after refresh. For example, if the user sets first Notification menu to ON, then after refresh only this toggle is ON, email toggle is OFF and viceversa.