I know shutters aren't supposed to be lubricated, but I've had luck on old gummy ones by hosing them off with zippo lighter fluid. The fluid evaporates leaving behind only the slightest lubricating layer. I started doing this with my 10/22 triggers because any other fluid makes them gum up and no lubricant at all makes them feel harsh. I fixed a nonworking Isolette shutter just by giving it a lighter fluid bath; it's still working.