Thank you very much for the solution! I created a lot of sceneries in Europe (parts of Germany, Italy and France) with AeroScenery (always: Grid Square Selection Size: 9, Image Source: Bing, Zoom Level 17, AFS Levels 9, 11, 12, 13 and 14) without problems. Then came up the same probs with loading in patches you reported.
I changed the decimal format and put the Shrink TMC grid squares from default to 0.01 degrees. This seems to be the solution.
The most remarkable think is, that the processing time for one Grid reduced from approx. 9-10 hours to 2,5 hours with the same output quality! OMG, I wasted so much time with the wrong settings. Have you noticed too such a significant reduction in processing time?
I put "Write Raw Files" to "No", but with the setting "Write Images with Mask" I'm not certain. What does it mean? When do I need masks?