I had been struggling with print quality for quite some time on my mf726cdw, with colors printing very lightly. I updated the firmware and reset all settings recently, and to my surprise my prints all of the sudden looked fantastic!
Sadly, I enabled auto gradation adjustment on startup, and found that the adjustment brought my quality back to being super poor.
Recently, I discovered that trying to run the gradation adjustment procedure (both full and quick) fail with the message "correction failed" and I'm betting that it's also been failing at startup, resulting in the incorrect gradation settings being applied automatically.
I went through the manual which gives the suggestions:
The genuine toner cartridges have chips on them that provide the printer with toner level information and allows print quality adjustment. We can only suggest the use of the genuine toner cartridges since we have the specifications for our toner. Third party toner can cause print quality issues and problems with adjusting quality and performing maintenance functions.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.