Gear easily worn out on Toshiba e-studio45

Question

Good day!

The copy has been alright but occasionally the page darkens, what we do is we clean the screen and the corona wire near the drum because it also darkens.

I have another problem because the small gear (21 teeth) on the developer easily worn-out. I have just replaced it last june and it has worn-out in a month time. Does the gear worn-out easily or there is a reason why the gear easily worn-out.

I hope you could help me again. Thanks.