toning issues from processless plates

Our shop recently purchased a Screen Platerite 8100. It uses ultraviolet I believe to make processless plates. I understand that technically the press water system is the processor, but I am having some issues with toning. We have two presses, a Hantscho web press and a Ryobi 3304 H. The plates have worked well on the web press, but I am having trouble with toning on the Ryobi. I am using agfa plates. It is my understanding that several sheets must be printed after the water system cleans the plate to remove all the emulsion. My theory is that the web runs well because printing starts and continues in one step. Also on the web there is paper taking away any emulsion for the entire length of the plate. By the time small adjustments are made to get everything in register several hundred signatures have been printed and all is good. On the job I am trying to do on the Ryobi, the sheet is only about half the length of the plate. I have tried running 25-30 copies before shutting down to check register, but to no avail. I have cleaned my fountain cooler, then changed to the fountain solution agfa recommended for these plates and have also tried washing them by hand several times with the fountain solution before putting them on press.
Can anybody tell me what I am doing wrong?