I have rebuilt several cartridges and replace drum/toner/ blade/ chip. I have a few that have failed. Where rt side of copy has lines and is light and rest of copies look good. I look into this and found that toner plate that is to add toner to foam roller has a build up of toner so it doesn't supply enough toner to roller. The only way to clear it is to pull mag roller/ foam roller/ developer regulator plate. This will give you access to plate so you can vacuum it. Reason i know is from replacing each individual item and then testing till the problem went away.
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