Andrew...I found this on photo.net to match your problem....
John Falkenstine , May 21, 2004; 09:30 p.m.
(Ahem) I just took my Super Ricoflex TLR apart because all of the grease in the helix focus thread apparently has turned into something resembling loctite. careful swabbing using PEC-12 "Archival photographic emulsion cleaner" (smells like acetone mix and I wouldn't use it on film)gradually dislodged this scummy stuff, but a special very tiny flatblade screwdriver is need for total disassembly, so things are parked right now. Re-installing the bottom lens/shutter assy requires some care because even tho the lens is mounted tightly against the lensboard, there is a spacer right BEHIND THE front lens assembly which maintains enough clearance to allow freedom of movement of the shutter cocking/release ring. My recommendation is to take it to somebody who knows where all the parts need to go, or spend some time reading the manual so you can do it yourself. BTW I first thought this camera was a piece of frozen junk, but after a partial cleaning it is already looking much better. This would be a neat unit for adapting to 35mm. Have fun.
Sounds like it's a substantial job if you have to take the shutter mechanism apart. You could try the solvent recommendation and see if it frees up. Will keep looking for other sites I used to repair mine. Rgds, kal