Look to your gutters as well
I have the same leaky windows. Even after I scraped and re-caulked, I had 2 that would pour water onto the floor. I finally watched them in the rain, and discovered that the rain gutter above the window had an uneven join that directed water right onto the sill of the window. This constant splashing was spraying water all along the glass, and it was leaking in above the new seal.
For the very short term, I screwed some long screws into the join on the gutter - now the water runs along the screw and falls to earth 1.5" farther from the bus, missing the window sill. Sure, it looks pretty silly. And, I caulked the entire window.
Long term - I'm putting in eaves/gutters that can handle a reasonable volume of rain.