Lookup is not working in the New UX. The Lookup involves a sub-sub object (a grandchild object), but it fails when attempting to access a lookup value.
Summary: The customer has a fairly complex configuration with a custom Object that has two sub-objects, and those sub-objects each have a sub-sub object. When attempting to create an entry in the MUX for the sub-sub object, it fails due to an CMN-0009 Attribute has invalid Lookup Value error. If you attempt the same steps in Classic UI it works fine.
Expected Results: It should create the entry without issue.
Actual Results: CMN-0009: Attribute 'Custom Lookup' has invalid Lookup Value '5123456'
Workaround: None.
Release : 16.1.0
Resolved in 16.1.3 and 16.1.2.1. This was tracked as DE68923.