I cleaned the sensor yesterday, and last night's photos are fine. But, I really don't understand how the sensor gets blotches on it when it is sealed under glass. The only possibility I can think of is if the camera gets hot out in the Sun, and volatiles from the oil in the camera vaporize and then later condense on the sensor. I hope it stays clean for a while. It's a pain getting to it with the filter wheel attached.
