This artefact in the images is not related to any physical dirt or similar. It is very likely caused by a misalignment of the laser inside the Flash unit. This could have been caused by a rough transport for example. If you already tried re-calibrating it including the auto-alignment and it didn’t fix the issue, we need to do a procedure called “best beam find”, to get the laser in the correct position again. For this we need a special service software tool, a dose meter, a generator and some time, up to one hour or more if we run into issues during the best beam find. I will provide the service tool via remote.