Smudgy Prints

I have the same problem with mine. Under the roller assembly there is a box which contains extra toner that is wasted from the printing process. It needs to be cleaned out periodically. It's this extra toner that gets put back onto papers as smudges, etc. I took my entire printer to Cartridge World where they took the roller assembly out and put it into a machine that uses bursts of air to **** out the extra toner (mine was full). I asked him why he didn't just disassemble the box from the roller assembly and he said that there are sensitive electronics that if moved would have to be resoldered. He said it was easier to use compressed air to take out the extra toner. Believe me, it was a mess and I wouldn't have wanted to do it at home. His machine was made for messes.

Never touch or clean drum surface, they are higly sensitive.

If as I suspect what you are seeing is toner not being cleaned from drum properly, these drum units have a rubber blade that wipes the drum as it passes it, some non oki toners are very abrasive and wear these blades out, sometimes the rubber is effected by heat or age, some after market drums use inferior cleaning blades in drum construction.

Are your 4 drums and toners the OKI genuine ones or did you purchase aftermarket/refurb/recycled?

Wiping the drum has probally scratched it's photosensitive surface.