Lagrange<3> is broken
Lagrange<3> implements an edge-flip depending on the edge orientation.
The decision is is based on getting the edge vertices using ReferenceElement::subEntity
. Since their's no guarantee that the latter is consistent with the embedding of actual grid entities, this is likely to fail.
Unfortunately I currently cannot construct an example where it fails. UGGrid seems to automatically orient triangles in a consistent way which is possible in 2d. But in 3d and for surface grids one should be able to construct a counter-example.
Since we have to explain the above mentioned inconsistency regularly: Does someone has a minimal example of a grid where this fails?