Lightning out App Error in Flow

Question

I have a flow that is called from a List View. Works fine on one org, but when I built the same flow in another org, it runs, but below the flow it displays this:

Lightning out App error in callback function

The flow uses an aura component to provide a lookup field, and if I drop that element from the flow, the error is gone. I don't know how to troubleshoot/fix this error. Ideas?

 <aura:component implements="lightning:availableForFlowScreens" access="global">
       <aura:attribute name="sObjectType" type="String" required="true" />
       <aura:attribute name="lookupFieldName" type="String" required="true" />
       <aura:attribute name="lookupFieldResultId" type="String" />
       <lightning:recordEditForm objectApiName="{!v.sObjectType}">
           <lightning:inputField fieldName="{!v.lookupFieldName}" onchange="{!c.onChangeLookup}" />
       </lightning:recordEditForm>      
</aura:component>

({
    onChangeLookup: function(component, event, helper) {
        component.set("v.lookupFieldResultId",event.getParam("value"))
    }
})

 <design:component>
       <design:attribute name="sObjectType" label="Object API Name" /> 
       <design:attribute name="lookupFieldName" label="Field API Name" /> 
       <design:attribute name="lookupFieldResultId" label="Lookup Field Id (output)" /> 
</design:component>

<?xml version="1.0" encoding="UTF-8"?>
<AuraDefinitionBundle xmlns="urn:metadata.tooling.soap.sforce.com" fqn="FlowLookupField">
    <apiVersion>45.0</apiVersion>
    <description>A Lightning Component Bundle</description>
</AuraDefinitionBundle>

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UPDATE

I eliminated the element from my flow, saved, activated... no error. Then I added it back to the flow, saved as new version, it works, no error.

Any ideas what's at fault?

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SECOND UPDATE

A day later, no change to the Flow, but I'm getting the error again. Literally, no change -- it's still active from yesterday. (!)

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THIRD UPDATE (a couple weeks later) I have filed a Support Case with Salesforce, and they've now escalated it twice. Waiting to hear... then I'll report back.

Answer 1

This ended up being filed as a Known Issue: https://success.salesforce.com/issues_view?id=a1p3A0000003dFeQAI

However, I think I've solved it. I went to SETUP > Process Automation Settings and selected Enable Lightning runtime for flows. Now the issue is gone on the two orgs I've tested.