I had flashing repair work done around one of three windows in my bedroom last summer. When it started getting cold, I noticed moisture / condensation on one of my windows. I thought it would go away in a few days; it did not. There is continuous moisture on the main window where the work was done. I've been in my home 10 years and have never experienced this problem. And, there is no moisture on the other two windows in my bedroom or on the three windows in my adjoining bathroom. I am wondering if the flashing work could have caused this problem.
Did the flashing repair involve removing/re-positioning the exterior trim/siding/sheathing?
If so, the simplest scenario might be due to the insulation being disturbed/removed.
You can check on the inside by moving a burning incense stick around the trim and window, which should reveal air movement. If you find a "windy" area, remove the interior trim and add low E foam (low expansion) if there are any air leaks.