Hi Ja,
Sounds like you have tried everything already, so it would be a hardware escalation. Please call support to request a technician at: 1-800-821-2797 or 1-800-835-6100
All are about 1/2 full and had been working without a problem since installed about 6 months ago. I have re-booted, unplugged for a time to clear memory, tried firmware updates, re-installed the cartridges, etc. without any change. I assume it is software or sensor/board related but am looking for insight on what to try next. Thanks!