Recently I observed reflections in a double-glazed window. I wondered that the double reflections were not the same if I changed my point of view. For example the two images of a candle would overlap at a certain angle but separated when I moved. The only idea I had to explain this behavior is that one (or both) of the glass panels was not totally plane but curved. Does that sound plausible or is there another explanation for this behavior?
No, the effect is due to the difference in depth between the front-surface reflection and the rear-surface reflection. Draw the "unfolded" optic axis between you and the candle, and you'll see that as the angle that ray path makes with the window changes, the difference in the apparent position of the candle changes as well. Here the dotted lines represent the apparent line-of-sight to the object.