My glasses are so thick they could start a fire in the sun. I once tried that trick and accidentally called out a fire hydrant. It just stood there, judging me. My optometrist said my prescription is a cry for help.

Could it be a tiny bug or spider web on the outside of the glass you can't see? They're really good at spotting that stuff... my window looked clean until I got up close and saw the tiny bugs.

Thermal water spray is a game changer for that.