Invalid Observation invariants us-core-3 and us-core-4 on:

• us-core-3 http://hl7.org/fhir/us/core/StructureDefinition/us-core-smokingstatus
• us-core-4 http://hl7.org/fhir/us/core/StructureDefinition/us-core-observation-lab
• us-core-3 http://hl7.org/fhir/us/core/StructureDefinition/us-core-observation-clinical-result

1. Gist is that they are all on the context of the value property and then the expressions try and walk into the value property on that
e.g value.ofType(Quantity).system.empty() or value.ofType(Quantity).system = 'http://unitsofmeasure.org'
should be
ofType(Quantity).system.empty() or ofType(Quantity).system = 'http://unitsofmeasure.org'

(not repeating the value at the start as already on that node)

2. to address the warning 

warning

us-core-4: The left side is inherently a collection, and so the expression 'ofType(CodeableConcept).coding.system = 'http://snomed.info/sct'' may fail or return false if there is more than one item in the content being evaluated

 change from :  ofType(CodeableConcept).coding.system.empty() or ofType(CodeableConcept).coding.system = 'http://snomed.info/sct'

to ofType(CodeableConcept).coding.system.empty() or (ofType(CodeableConcept).coding.system contains 'http://snomed.info/sct')