I suggest you contact http://www.hlehmann.co.uk/ (spares@hlehmann.co.uk). They were very willing and sent me the part (cm1-7226-000 foc assy top) outside the UK. It is not difficulty to change the part in your camera.
That is faulty part
I thought that I should add my comment as I had this same shutter problem as well. Too often we forget the forum which helped us out, once our problem is gone. Here's my story to date:
I bought my S100 as early as I could in Jan 2012. I love the thing! However after 10,000 pictures it had the well-known lens problem. I sent it back to Canon (Canada) and they said getting lens assemblies was slow at the time, so they destroyed my camera, revoked the serial number and included a brand new camera in the box (obviously less the battery, charger, strap and cord). Fine service - and I certainly appreciated it!
Ten thousand pictures later and the new camera developed the bad shutter button. It started to slow down, then quit entirely (same story I have read here a number of times). I read the forum and decided I wouldn't try Canon service this time as the camera was nearly three years old. The Deoxit plan sounded plausible, so I headed out to a music store and spent $29 plus 14% tax on a can of Deoxit F5 for conductive plastic faders (slide volume controls on audio control boards). I told the sales guy I only needed one drop of the stuff, but he showed me no mercy!
I carefully removed both case halves of the camera and sprayed Deoxit on the end of a jeweler's screwdriver. Next I pushed the white membrane on the top of the switch down with a lead pencil, while dropping in about one drop from the screwdriver. It didn't look hopefull at first, but after I worked the membrane up and down a few times I noticed the liquid was pumping out at the base of the switch onto the flexible circuit board. Great! - I now knew it had penetrated both sections of the double switch. I quickly soaked it up with a facial tissue until it stopped. Then I reassembled the camera. I couldn't believe it worked perfectly right off!
That was on Dec. 12, 2014. Since then I have taken 1,300 shots. In the early days after the fix, there was occasional hesitancy and I feared it would soon fail again. However this has not been the case and gradually it seems to be getting better and better with use. At this point a month later I hardly ever experience a slow shutter response when pushing the button. I have had a lot of experience with cleaning delicate electrical contacts in my work and hobbies for more than fifty years. My experience is that after cleaning, the component will either fail again soon - or go on "forever". I try to use the S100 every day or two - I believe this helps - especially in the early days after cleaning.
This repair is not a job for anyone, but there lots of young people who are good with smartphone repairs who should be quite able to handle this job. Oh yeah - some old guys like me can do it too!
However if anyone tries this they do it at their own risk...there are plenty of things that could go wrong. I am only telling my story and how it worked for me. I am not giving instructions or recomondations.
I am including a picture of the innards of the camera showing the shiny metal switch with the round hole on top revealing the white membrane where I applied the cleaner.
Thanks to this forum for helping me get my prized camera working again and best of luck to anyone who gives it a try.
John
