explicit-hyperc-tris and explicit-hyperc-quads failing on Intel

explicit-hyperc-tris and explicit-hyperc-quads fail tests on Intel:

explicit-hyperc-tris: Assigning tracerbehindfront = [[ 0.]]
explicit-hyperc-tris: Running check volume fraction behind front is 1.0 (relaxed for simplex elements):
explicit-hyperc-tris: failure.

explicit-hyperc-quads: Assigning tracerbehindfront = [[ 0.]]
explicit-hyperc-quads: Running check volume fraction behind front is 1.0:
explicit-hyperc-quads: failure.

Cian - please could you take a look and see if there's anything obvious needing fixing/tweaking here?

** This bug is targetted to be fixed before 4.1.11 is released