Changing the shape of a group does not update group colours correctly

Open an alignment and create a group, giving it a Blosum62 colour scheme. Now resize the group to a smaller extent (both x and y) and back to the original extent - all seems ok, colours follow resize. Now resize again to a smaller extent (both x and y). Residues to the right of the resized group have their colour updated, but residues below the resized group do not.