I'd recommend you stay away from pouring lube into the camera. I realize your intentions are pure but graphite can get all over the place.
If you remove the bottom cover, you should be able to see two magnets. The larger one is the release magnet,(towards one end) smaller one(near center) is closing curtain magnet. if you can get to the suface the armature contacts try cleaning it with a strip cut from a $1 bill soaked in alcohol(strip should be 1-2mm wide) if you're well of you could use a $100 bill.
Place the wetted strip between the armature & mg. hold the arm to the mg with a tweezers or dental probe & pull the strip out.(repeat 2-3 times)
If you can access the solder points you can also resolder them. Sometimes the contact just goes bad.
You can test your fix be "exercising" the camera with the back open & observing the shutter operation.(lens off will make this easier) Use a speed slow enough that you can see if the shutter fails to time out. 1/30-1/125 if it works you'll see light through the shutter aperture. If it fails you'll see nothing but black.
***Important***If you resolder the connections. REMOVE THE BATTERY FIRST!!! If the batt. is left in there is a possibility to ZOTZ the main board.
Disclaimer-- I'm working from old recollections there's a possibility I'm misremembering exact layout.