gday Mel - I have had one a few months now and I have to admit I have never seen what you are describing. I have attached a unprocessed lunar image taken one weekend at the observatory when I couldnt stand sitting watching TV with the boss and decided to go play in the obs. It is a raw light straight out of the camera just stretched to 8 bit for jpg conversion - no other processing (obviously - its not real good
).
It was a.005 sec image taken through a ED120. So in short I dont have an answer for you but if you want me to reproduce your exposure, scope etc I will have a go this weekend (We have a couple of hours to moonset)
Do you have an image of of the anomally - hopefully by reproducing the whole set up (A mate has a Skywatcher ED80) it will show if it is just your camera or is general thing of the camera and exposure time etc.
MB