As it can be seen in the screenshot below, the Layers window is wrongly placed, although it is considered docked.
The intended position is to the left of the Colors window (this one is currently docked to the top-right of the window), which is where it was snapped-to in previous versions of paint.net
Running paint.net 4.2.7 on windows 10. Happens regardless of monitor dpi and window size. Did not happen in previous versions of paint.net (namely in 4.2.6 alpha/beta versions)
Further testing: Trying to dock a window to the corner or one side of the window results in erratic movement, and offscreen window movement.
Workaround: For some reason trying to reset the windows' position fixes this, although the first time trying this results in the window being placed wrongly.