I am using the online tool for R4.
The result there says 0 requests were made, so I'm wondering if this error occurred before the request was even made.
Error Message: Fatal Error: undefined method `occurrenceDateTime' for #<FHIR::Procedure:0x00007fa6ced57678 @id="5d3a089b72e89ba0945a1ef6", @meta=#<FHIR::Meta:0x00007fa6ced56688 @id=nil, @extension=[], @versionId="1", @lastUpdated="2019-07-25T19:53:02.557+00:00", @source=nil, @profile=[], @security=[], @tag=[]>, @implicitRules=nil, @language=nil, @text=nil, @contained=[], @extension=[], @modifierExtension=[], @identifier=[#<FHIR::Identifier:0x00007fa6ced55be8 @id=nil, @extension=[], @use=nil, @type=nil, @system="http://terminology.bluebuttonpro.com/identifier", @value="6e111e681224433592ac6baa5a451b68_5d3a089b72e89ba0945a1ef6", @period=nil, @assigner=nil>], @instantiatesCanonical=[], @instantiatesUri=[], @basedOn=[], @partOf=[], @status="entered-in-error", @statusReason=nil, @category=nil, @code=#<FHIR::CodeableConcept:0x00007fa6ced555f8 @id=nil, @extension=[], @coding=[#<FHIR::Coding:0x00007fa6ced550f8 @id=nil, @extension=[], @system="http://snomed.info/sct", @version=nil, @code="1698001", @display="Ulcer of bile duct", @userSelected=nil>], @text=nil>, @subject=#<FHIR::Reference:0x00007fa6ced54a40 @id=nil, @extension=[], @reference="Patient/5d3a089b72e89ba0945a1ea9", @type=nil, @identifier=nil, @display=nil>, @encounter=nil, @performedDateTime="2017-09-10T08:15:49.0000000Z", @performedPeriod=nil, @performedString=nil, @performedAge=nil, @performedRange=nil, @recorder=nil, @asserter=nil, @performer=[], @location=nil, @reasonCode=[], @reasonReference=[], @bodySite=[], @outcome=nil, @report=[], @complication=[], @complicationDetail=[], @followUp=[], @note=[], @focalDevice=[], @usedReference=[], @usedCode=[]>