TinTin, one test to identify a sticky shutter is to leave the camera body in a dry, warm place overnight (an airing cupboard works well) and then shoot a roll immediately after removing it.
I have one of those Oris mechanical "automatic" watches that winds itself as you move around. I didn't wear it for a few weeks but, when I finally put it back on my wrist, it ran slowwwww. I happened to mention this to one of Oris' servicing dealers and he suggested the airing cupboard test. I wasn't convinced, initially, so I mentioned it in passing to a friend who repairs cameras. He said it's a trick camera repairers also use to see if it's nothing more than the camera / lens lubricants that have gunged up.
After 24 hours in my airing cupboard and a few hours walking about, my watch is back to perfect.
I'm not saying that this will definitely work but it's worth a try - especially if you haven't used the camera or had it CLA'd for a while.