There is a condensation-free area that is shaped like $3/4$ of a bell curve. I’m guessing warm air is leaking to the inside, on the bottom, below crest, and also adhering to the edges, preventing temperature gradient needed to allow condensation. But I can’t see anything to confirm this.
Please check if there's more gap in the farthest down-right part of the window, between the glass and threshold.
As the room cools, it lets more air to pass through that passage, and causing a convection current within that small region. This creates a pattern almost like a Gaussian distribution, as in that region, air cannot condense, as its circulating due to convection current in the hot-cold air transition area.
