In MUX, when selecting a Booking Status on a Staff member, the option "Mixed" is present. If you select "Mixed" it will produce an error
STEPS TO REPRODUCE:
1. Log into the New UX interface. Open a Project.
2. Go to the "Staff" section.
3. Add a Resource, or if some are present use an existing one.
4. Double click on their "Booking Status", you'll see three options "Hard", "Soft" and "Mixed". Select "Mixed"
5. An error is received: "CMN-0009: Attribute 'Booking Status' has invalid Lookup Value '10'" and the value reverts.