Issue
The print is uneven.
Cause and solution
The toner cartridge is almost out of toner.
Take the toner cartridge out of the printer, shake it gently 5 or 6 times to evenly distribute the toner, and then reinstall the toner cartridge.
If this does not solve the problem, replace the toner cartridge with a new one. [Replacing the Toner Cartridge]
Cause and solution
Paper is too moist or too dry.
Replace the paper with new paper in an unopened package. [Usable Paper]
Cause and solution
The drum in the toner cartridge has deteriorated.
Replace the toner cartridge with a new one. [Replacing the Toner Cartridge]