I have an E M5. About 6 months ago I noticed serious sensor pollution well within the warranty period. I investigated the options. Inevitably, asking for other people's experience on internet forums produced a blizzard of contradictory responses (what did I expect?) But at least one user online reported that he'd successfully wet cleaned the sensor himself, IBIS notwithstanding.
The Olympus dealers who supplied the camera offered to clean it for me as a chargeable service although they came up with at least 3 different sets of prices and turnarounds. Olympus indicated that it was a return to factory requirement and not dealer serviceable: I suggested they notify dealers of this fact. Jeeze! I returned it to Olympus who sent it to their Portuguese centre.
It came back two weeks later, as promised. A few hours later I took it out and shot some casual snaps. The camera began behaving extremely unstably within a couple of dozen actuations - freezing up in a variety of different ways as well as various other weird manifestations. I tried a range of tests including using different lenses and warm-up periods as well as playing around with operating modes however I could detect no obvious correlations. I called Olympus and, of course, was asked to return it. Each courier visit eats up at least half a day.
When I got it back it began behaving oddly almost immediately although not quite as severely as previously. However I noticed that the sensor was covered in dead pixels which could even be seen via the EVF! I called Olympus and was asked to return it again. Cue impotent fury.
Eventually after clawing my way up Olympus' European food chain I managed to get the camera swapped (as I'd repeatedly requested) for a new replacement - after all I'd sent in a perfectly serviceable camera which they had broken and failed to rectify. To Olympus' credit they gave me an extended new warranty by way of compensation. Two months of headache. At least my D700 got some exercise.
Sometimes even taking the safe option doesn't necessarily work out as planned.