On a whim and for what it's worth! I had a somewhat similar problem with one of my two X700's. Mine wasn't a capacitor problem though. I wish it would have been because I would have fixed it! I could physically move the advance lever, but it wouldn't cock the shutter at the end of the throw. I found that occasionally if I would press in on the film release button on the bottom that it would help out. Why, I really don't know. After sending the camera to Morgantown Camera and Video repair I was informed that it had something to do with the spring mechanism attached to the advance lever. All in all it was well under $100 for shipping, the fixing as well as a cleaning. I think it was around $75.
Also, if your still interested in it I have a factory repair manual for the X700 that I got off ebay a couple years ago. It's great! I never got the chance to really use it as it was more detailed than I would have ever imagined, but on the same token it was kinda cool to see the schematics and exploded views. Good because it lists part numbers!
Anyway, hope all goes well with the camera!