Some comment has already been made about the relative merits of robustness and accuracy, and the need to solve more complex problems by gradually increasing the complexity of the model, but they are worth reiterating here. Generally speaking, higher order discretizations are more accurate but less robust than lower order ones. Increasing the order of discretization by increasing the Blend Factor should be approached in the same way as increasing the complexity of the physical model, that is, gradually, and by starting from a more robust solution.