There is a sensor in the scanner that is picking up the sun light coming in through a window, which activates the "hunt". I had this happen to me at a certain time of day when the sun was beaming in through the window.
Just about every day in the middle of the day, the scanner on my 8560 MFP starts to "hunt".
The lamp stays lit and moves about 2 inches then back again. This continues until I lift the lid and keep it open for awhile.
Is there an overheating issue with this printer?