I've been having water leaks around all 12 of my replacement windows for months now. Windows have been re-wrapped and caulked, siding checked, and still, they leak. Today, someone said to see if the jamb is caulked/sealed to the window sill. I never heard of this, and there's no information about it online. However. I looked and sure enough, not on the window jambs are sealed where they meet the sill. Can anyone confirm if this is an accurate assumption that they need to be sealed?

Just for some background info, the original owner did the windows himself before we bought the house a year ago. All of the caulking had since cracked/warped/came of, so we assumed the new leaks were because of the use of poor quaulity caulking. Now, thousands of $ later and we still can't figure out the leak!