Dataflow Gen2 w/ Variable Library - variable resolves but fails in destination query

[merganzeruncle]

I'm trying to create a Dataflow Gen2 that uses a variable library to remap the destination lakehouse between stages of a deployment pipeline. I followed these two guides:

https://learn.microsoft.com/en-us/fabric/cicd/variable-library/tutorial-variable-library

https://learn.microsoft.com/en-us/fabric/data-factory/dataflow-gen2-variable-library-integration

I have created a variable library with entries for WorkspaceId and a LakehouseId. 

I have two queries for WorkspaceId and LakehouseId in my Dataflow. These appear to be working. Just as a test, I added another query that writes these to a (hardcoded) lakehouse destination, and the data that appears when I run this is correct (the correct Workspace Id and Lakehouse Id).  

However, when I try to use WorkspaceId and LakehouseId in the destination query of one of my actual data queries, I get an error "The key didn't match any rows in the table".  

Here is the m script for the destination query that fails: 

let
  Pattern = Lakehouse.Contents([CreateNavigationProperties = false, EnableFolding = false, HierarchicalNavigation = true]),
  Navigation_1 = Pattern{[workspaceId = WorkspaceId]}[Data],
  Navigation_2 = Navigation_1{[lakehouseId = LakehouseId]}[Data],
  Navigation_3 = Navigation_2{[Id = "Strong", ItemKind = "Schema"]}[Data],
  TableNavigation = Navigation_3{[Id = "Destination", ItemKind = "Table"]}[Data]
in
  TableNavigation<p>

(To clarify, that ID="Destination" is because the destination table name is also incidentally called "Destination" for unrelated reasons)

This was generated by using the destination lakehouse widget on the query, but then I replaced the hardcoded workspace Id and lakehouse Id with my variables. Other potentially relevant information - the destination lakehouse is schema-enabled. These queries don't use incremental refresh, although I have another Dataflow that I need to do this in that does use an incremental refresh.