Every time (I'm thinking approx 5 times in 10 years), the print quality has been sub-par. 4 times I've replaced the refilled toner with genuine and the issue was sorted. Once I had to replace the drum unit as well to restore print quality.
I had 6 years in the toner reman industry.
Refilling/re-manufacturing can be done with good results , but they are NEVER as reliable as genuine.
Although, some toner carts are so badly designed or so weird they are too problematic to recycle & just fail .
Even some genuine toner carts had a huge fail rate : judging by the amount of toner left in them.
It comes down to cost to do it properly. Possibly why the Chinese reman imports are so damn awefull.
I recently bought a remanufactured toner for our old LJ5 , one of the easiest to reman . It was a 100% fail (had several issues), must have been a chinese import.