I think you are not giving enough agitation. My experience with the quad is that I had to give continuous agitation. I increased the temperature to 22c and reduced development accordingly, about 75 seconds, and agitated continuously in a circular/oval configuration and occasionaly lifted the print upwards out of the slot about 60% of the length of the paper. I increased the temperature to help produce a warmer print colour. I don't think the developer is a problem, I used many different types and never had the problem that you describe.