Only a few parts of the shutter mechanism need to be oiled. And certainly not greased. There are watch maker's oils of very high quality (Moebius 9010 comes to mind) that really never freezes. However if even that low-viscous oil enter the shutter blades your in for trouble. If this is an oil issue you are having bad luck or a bad CLA (wrong oil). The mechanism can of course also be slowed down by humidity in it before being brought out into the cold.
Originally Posted by Mainecoonmaniac