There's no lube applied to any portion of the aperture blade system.
There is lube in the focusing helical, and it has to be thin in order to autofocus.
What's happening is the lube is heated and then either migrates to the aperture system or evaporates and condenses on part of the system. Because of the surface tension on the blades or blade operating ring/housing there's not enough muscle in the system to move it.
What any technician will do is remove the blades & clean the blades/housing/ring reassemble & consider it fixed. Unless someone comes up with a lube that is of low viscocity that doesn't migrate this will continue to happen.