Just wanted to come to this post and share what happened with me. I had the "half stuck" shutter problem, and not wanting to lose my camera for three weeks AND spend hundreds of dollars, I tried the contact cleaner from WD-40 for $16 on Amazon.
The first try fixed it for about 100 shots. Noting that there was an improvement, I tried again. This time, I'm past about 200 shots and it's working perfectly.
How I did it--take out the battery and memory card, spray the CONTACT CLEANER (not regular WD-40) into the little gap where you can get a liquid into the shutter button. I sprayed more than you would think, but not enough that it would be like pouring a liquid into the phone. I then pushed the button continuously to try to loosen up any dirt in the button. The first time worked a little bit (I thought it worked perfectly until the problem came back at about 100 shots and several lenses). The second time I did a little more and it's been just like new ever since (about 200 shots or more since then). I'll continue to post updates, but having seen this thread and trying the contact cleaner . . . I have to say try this first. It certainly didn't harm the camera and it was a lot cheaper than fixing it. It must be some grease or dust that got into the electronic connection. WAY better than sending it in for $200+ repair.
Of course, it could come back--and then I can still choose to send it in, but to fix the whole problem (for now) for $16 + 2-day prime shipping . . . and it's day and night between the spray and before, so I'm not seeing that it could be a bigger problem than the button connection itself, regardless of a repair company saying they need to replace the motherboard. All this, and I didn't even open one screw on the camera.