Hoping to make it into the R4 technical correction:

Element ids in profiles such as respiratory rate (http://build.fhir.org/resprate.profile.json.html) use type slicing but render the ids incorrectly:

{ "id" : "Observation.valueQuantity", "path" : "Observation.valueQuantity" }

should be:

{ "id" : "Observation.value[x]:valueQuantity", "path" : "Observation.valueQuantity" }

according to the third bullet here:

http://build.fhir.org/elementdefinition.html#id