A few days ago I took photos of a nice curvy business center in another city. Later I discovered that many frames had weird artifacts on the glass, shown below as 100% crops.
An almost normal shot:
A spotty shot 46 seconds later:
A striped shot 9 minutes earlier:
All crops show the same windows.
I did check the sensor, it was clean. I used a CPL filter to control reflections. Unfortunately the artifacts are too small to notice on camera LCD without zooming in, so I did not notice them and did not experiment to lose them on spot.
What could have caused those artifacts and how could I prevent them in future?