Then lift it off and keep it to one side.
Anderson skylight window leaks.
Our new anderson skylights leak.
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.
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.
Two years later after a downpour one of the other skylights developed a leak.
To fix a leaking skylight.
They leaked brand new.
It is pre molded seamless and waterproof polyur.
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.
Sloped glazing such as roof skylights probably has historically had more leaks into the roof structure due to improper roof flashing than other window failure causes.
Anderson rep said seal was defective.
Original installation squareness.
Start by checking that the windows are basically square in the frame.
With a scraper slowly remove the weather stripping around the skylight cover and the curb.
Take a moment to seal any cracks you find on the cover with the clear silicon caulk.
Leaks at skylights left unattended can lead to costly structural damage rotted roof sheathing rotted roof framing and wet moldy insulation as well.