Comment (by Samuel Cupp):

So, in answer to the original question, you can try changing the schedule.ccl to what I posted above and see if that resolves the errors or not. I haven’t run with mixed-warning much, so there might be some other cases that could trigger it that I haven’t thought of.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2723/no-boundary-conditions-registered-for