They leaked brand new.
Anderson skylight window leaks.
Two years later after a downpour one of the other skylights developed a leak.
With a scraper slowly remove the weather stripping around the skylight cover and the curb.
Our new anderson skylights leak.
Original installation squareness.
1 lift up the shingles next to the skylight one at a time and brush out any dirt and debris.
Leaks at skylights left unattended can lead to costly structural damage rotted roof sheathing rotted roof framing and wet moldy insulation as well.
I also see water stains on the bottom of the wooden window frame suggesting there has been wind blown rain or snow melt leakage too.
At the time of installation 3 years ago our contractors had a anderson rep out to replace seals in 4 or 5 of our brand new skylights.
2 using a caulking gun loaded with a tube of roofing cement force the mastic up under the shingle where the metal flashing meets the roofing felt the thick black paper under the roofing material.
I think your anderson slider window has more than air leaks.
Take a moment to seal any cracks you find on the cover with the clear silicon caulk.
It is pre molded seamless and waterproof polyur.
Unscrew the fasteners holding the cover of the skylight window on with an appropriately sized driver.
Anderson rep said seal was defective.
Then press down on the roofing shingles to seal them tight.
Then lift it off and keep it to one side.