The reason for your problem may be: the setup of lattice for the 4x4 supercell is given by a customized way (see below), rather than the embedded Hexagonal() of Bravais lattices. So you can choose only "G, Z" in the Brillouin zone route in the "Band structure" analysis for the customized lattice.
# Set up lattice
vector_a = [4.9224, -8.52584689518, 0.0]*Angstrom
vector_b = [4.9224, 8.52584689518, 0.0]*Angstrom
vector_c = [0.0, 0.0, 6.709]*Angstrom
lattice = UnitCell(vector_a, vector_b, vector_c)
You can replace the above setup of lattice by "lattice = Hexagonal( a= 4.9224* 2 * Angstrom, c = 6.709 * Angstrom)". For the lattice defined by the embedded Hexagonal(), you can choose more special k points for the Brillouin zone route in the "Band structure" analysis.