That looks odd, as if the monitor was mounted upside down (I've seen that issue many times but it was on the top).
Check if modifying this in mame.ini makes any difference:
monitor custom
crt_range0 15625-15750, 49.50-65.00, 2.000, 4.700, 8.000, 0.192, 0.192, 1.024, 0, 0, 192, 288, 448, 576