I’m working on a new-to-me 9900 and am running init. fills to prep the printer for PiezoPro inks. Occasionally, I’ve had an issue where upon powering on, I will get a cartridge error in every color slot. Turning the printer off, and then on again has always (so far, anyway) corrected this. Additionally, when powering down (and occasionally during cleaning cycles) the cartridges emit a kind of hissing / squealing sound. I know these carts are pressurized by the printer, but is this sound normal? The combination of the two events makes me think I have a bad seal somewhere, but the printer seems to be functioning fine otherwise. I have searched the forum and have found reports about many sounds, but nothing that sounds like this.
Thank you all!