We have this type of leak too. From behind the Sheetrock and on to the subfloor. The GC removed all interior Sheetrock around the window. Still no idea. A few days ago I stepped on two stacked paint cans and noticed our transom glass and the frame around it wasn't attached properly just by a millimeter on one side. I'm guessing that's our culprit. Hopefully. No one else looked there. I'm the shortest by 10". Good luck.

We are having the same the oroblem. Our first floor window lieaks above the top from the frame. This 1st story window is directly below the 2nd floor window. We have caulked the second story window and caulked the brick mortar. It still leaks when we have a blowing rain, The first level window frame is slightly damaged but the window above it is fine, It has to be coming from the 2nd floor because the first level has a nice dry wrap around porch protecting it, Thanks

"if you are getting water from your roof or from behind the siding for that matter, you will get water through any window opening regardless of how well its sealed." That would mean flashing is useless. The whole point of flashing is to keep water that has penetrated the siding from entering the house at the window. All exterior claddings pass some rainwater.

Photo with new stucco, leaks only with heavy rain AND wind. Only the three downstairs windows, slider and small window are the worst. Roof is less than a year old. Last night we had a good rain but no wind and there were no leaks.