Bistable azimuthal nematic alignment has been produced in channels with one flat and one triangular shaped grating sidewall with a small blaze asymmetry. Two frequency addressing has been used to switch between the bistable states. It was found that the time needed to latch to the other bistable state decreases as the voltage is increased. Surface defects move towards each other along the grating sidewall during the switching pulse. If these defects annihilate before director reorientation tilt-wall loops collapse in the bulk then it is possible for the loops to move away from the surface and to collapse in the bulk of the channel.