I'm surprised a GND that pricey would give you issues, although I don't know much about that brand. I use B&W MRC filters and even though I've experienced some minor flaring in direct sunlight shots, it's been minimal and easily correctable. I've never had the issue with the washing out like you did. That's also somewhat correctable. I played around with the shot a bit. Hope you don't mind. I took out the flaring and toned down the washed out area. I also cropped the sign and tail end of that car from the right side.