The interior is probably very sensitive to dust. On the inside of the viewing lens located at delivery dust particles of different sizes, which can be also not blow out. Since the device can not be opened, the dust can not be removed in other ways. As one would technically certainly can do something, especially since the price is not a bargain price level. The enlarged representation of the slides was also disappointing, we had actually imagined something bigger, well. We will keep the device nevertheless, for lack of alternatives.