Comment (by Erik Schnetter):

This might be an actual bug in Carpet. Or it might be that these barriers haven’t been tested in a long time, and don’t conform to Carpet’s communication algorithms any more.

I would be careful activating these barriers, they might just be incorrect these days.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2717/conflicting-barriers-in-carpetlib