Here is part of one of the odd images that was collected on our JEOL JEM 1010 in February, 2016, just a couple of hours after a series of "good images" were collected:
Odd CCD Image from JEOL JEM 1010 and Gatan CCD Camera
These patterns change over time (within 10's of seconds) and occur whether the electron beam is on the sensor or not. We also know that the patterns appear whether or not the camera is actually connected to the camera controller box or not, so this is not an issue internal to the CCD camera.
We eventually replaced this broken Gatan UltraScan 890 CCD camera system with a used Gatan MegaScan 794.