A possible cause may be that appropriate paper is not used or the amount remaining in toner cartridges is running low. Check the following.
Are you using appropriate paper?
Check usable paper, and replace with appropriate paper.
Do toner smudges and splatters appear when using the machine in an environment with low humidity?
Change the setting for <Low Humidity Mode>. The improvement effect is stronger with <Mode 2> than <Mode 1>. First try with <Mode 1>. <Adjust Image Quality>
NOTE
If <Low Humidity Mode> is specified, print density may be lower or uneven when the machine is used in an environment with high humidity.
Is the amount remaining in toner cartridge running low?
Regardless of the displayed toner level, the toner cartridge may have reached the end of its lifetime due to the machine's environmental conditions and the deteriorated materials in the cartridge. Replace the toner cartridge. Replacing the Toner Cartridge
