Can it be your exposure time is set to more than 3 seconds? I think I remember that is the threshold for the OM-D to take an additional shot with the shutter closed to determine "hot pixels". During that time you see the message you describe,
Olympus OM-D E-M10 Mark II Troubleshooting: “If the shutter is in need of replacement see the guide.” Is there a separate guide indeed? I can find a guide to opening a E-M10 but as far as I can see it does not bring me to the actual shutter?