After replacing the developing unit iR2270/iR2870/iR3570/iR4570/iR3530.
Execute the following service mode items:
Copier > Function > Install > STIR-K
Initialize the following service mode items:
Copier > Counter > DBRL-1 > DVG-CYL
A test copy that is made right after the toner has been stirred can be soiled on its back with a small amount of stray toner.
The sympton will likely disappear when 3 or so copies are made.