I think the supplier for these changed. We have not had any issues with the compatible toner cartridges for our Xerox machine before, however the last two batches of the toner caused too many problems: cartridge not being recognized, colours being off, culminating with issues with the developer unit. These problems did not start until the cartridges from the new manufacturer have been used. Since we saved a pile of money using compatible cartridges, I cannot really complain too much. However, until the manufacturer for these changes again, we will have to use genuine toner, as much as it pains me to say.