I have a R2880 that I use for PiezoDN. Printed a negative the other day that had banding so I did a couple head cleanings and a nozzle check. Everything looked OK except for the (yellow) K7 channel. I could not see any lines so tried a couple more had cleanings. Same result.
Then I pulled all the cartridges and did a flush of that channel with PiezoFlush, as well as cleaned the capping station, etc and did a scrub of the heads. Same result nothing through the yellow channel. Since I had a new spare cartridge I filled it up and replaced it Still same, nothing is showing through the yellow K7 channel.