Translation settings for system fields can't be unlocked

Overview of the issue

When adjusting translation settings in WPML → Settings → Custom Field Translation → Show system fields, you may might not be able to unlock a locked system field.

As a general rule, you should not unlock these, but if there is really a need you can follow the workaround below until this is fixed.

Workaround

Follow these steps by going to WPML → Settings, scrolling to the Custom Fields Translation section, and selecting Show system fields.

1. Click the lock icon to unlock the field that you want to unlock
2. Click the Save button for these custom fields
3. Refresh the page
4. Click on the field again to unlock
5. Click on the Save button to save the custom fields