I have been looking around for a Super-Angulon 90 f8. Before I buy.... It seems a common trait of the Synchro-Compur shutters that often come with this lens, that the slower shutter speeds are often sluggish or not working. I'm fairly handy, and not afraid to take stuff apart, but I am not a repair guy either. Is this problem usually a quick fix with some lighter fluid, or a more involved repair?....Generally speakng of course.