I was very careful not to push too hard on the syringe because of previous warnings about it. I bought this printer on eBay and after complaining about all of the colors being clogged, the user said he hadn't used it since April, 2014 and not all of the cartridges were in place when I got it.
At least you confirmed my suspicions. As I stated earlier I have another R1800 printer that developed a fatal error condition but at least the nozzles work. In that one the flush does not squirt out of the other nozzles.
I don't know how seals work between colors but I am wondering if replacing the manifold (the part with the ink ports) would work. I have the R1800 manual which shows replacing the manifold is not too difficult.