Patrick, As best we can remember, the "slats" in the inlet cover should be 90 dgrs. and straight across the opening. Make sure it's installed properly and turned as far as possible clockwise. Since the water inlet isn't coated with sediment or debris, the "splash back" from the air gap in the inlet housing
would be due to water flow/pressure. A couple of things to try: replace the water inlet valve, the replacement valve may be more tolerant(opens slower) and may stop the splash back. You can also turn off the water supply under the sink. Open the shut off valve one turn at a time, until the dishwasher fills without the splash back. We don't think replacing the water inlet assembly would solve the issue, especially since everything appears OK in the photos.