As the optimized 4th order second derivative operators have been proven to cause instabilities, simply call the minimal bandwidth operators regardless of parameter choices.

Note: The 4-2 second derivative operator was the only one to have an optimized variant. I suspect that it was never tested before. This makes the 4-2 second derivative operator behave like the -3 and 8-4 operators.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2860/dont-call-the-optimized-4th-order-second