I've just bought a Yashica Mat with a sticky shutter. I've spent the last few days flooding it with naptha and it works better now than it did, but it still sticks once the naptha has dried out.
It needs a full disassembly, thorough cleaning to get all the dried gunk out of the "dark corners", and fresh lube. I just started using ptfe grease on my shutters as I CLA them. I also got some Ptfe that drys to a dry film to use on speed dials where they rub against the shutter name plate and similar applications.
Stick with the watch oil, just a sheen, on shafts and bushings; extra fine powdered graphite on aperture and shutter blades, trace of light to medium weight grease where levers and springs slide against the case.
I use CRC Electronic contact cleaner as it is safe on plastics, rubber and leaves no residue. I spray the parts off over a small wide mouth jar then put the part in the jar with the cleaner fluid, cap tightly, let sit 5 to 15 minutes, swish, remove the parts, dry, lube, and assemble. On shutters like yours the parts may need to soak 30 minutes to an hour to come clean. Once I have sufficient fluid in the jar I just add the parts without spraying them first.
Part of the gummy gunk is micro fine metal particles from normal wear and dirt that came in from the control openings mixed into the dried oil and grease base. Flushing without disassembly only moves the gunk around in the tight places, aka dark corners. Flushing without disassembly is a stop gap measure not a long term repair.