Combining two questions in Dashboard chart behaves unexpectedly when "series breakout" present

In a dashboard, I am trying to combine two existing saved questions that share a common “time” dimension in a single chart.

  • The first question shows revenue over time, to which I am adding a “series breakout” showing the customer’s lifecycle at the point of purchase, and displaying as a stacked bar graph.

  • The second question is meant to be overlain, simply giving the user a line chart of total revenue in the same fiscal periods during the prior year for reference.

When I add the second question to the first via the dashboard, it stacks the second series into the first rather than keeping it as a separate line graph on the right axis as I wanted/expected. I have tried to modify the axis (setting second series to “Right” versus “Auto”) without success.

It does render each (first question as bar via left axis and second question as line via right axis) as expected if I remove the “series breakout” from the first question.

Is this expected behavior in Metabase? Any suggestion to retain the “series breakout” while overlaying the line?

The second question:

And the unexpected combination: