The "fixed" or "stack window" as they are called are easily fixed with Par bond sealer.
DO NOT USE RTV OR SILICONE SEALER.
Silicone sealers will not stay in place very long. Then when you find that the leaks starts all over, you cannot seal the area correctly, because the silicone materials created a barrier, as well as attracts dirt making the seal, dirt colored.
Simply clean the metal and glass junction. Apply Par bond to that metal glass junction.
Using Par bond is as simple as using tooth paste. If you smear it, wipe it off.
If you wipe silicone material off, it eventually will take on the dirt color. Ask Airstream. They learned the hard way.