This is the eighth attempt at this particular model, and the first time I’ve seen this particular problem. Is this a “temperature too low” thing, temperature too high, lack of support? I don’t think it’s a lack of support, since none of the angles exceed 45 degrees, and I didn’t have this problem on the last few.
Try using high extrusionwidths and print a bit slower (depending on the widths). For example 0.8mm on a 0.4mm nozzle. Works great for me!
Using any parts cooling fan?
missing/deleted image from Google+
Yes, I have a 40mm blowing down on it. Yours is definitely better than mine. 