Trouble with Weekend Rotation Schedule

Good Morning Everyone!

I've discovered a small problem with a rotation schedule I've been using. The sheet assigns a rotation of engineers to work a weekend day, without working two Saturdays or two Sundays in a row and rotating everyone about evenly. The problem I'm having is one instance when it reaches the end of *one* the rotations, it skips a Sunday entirely (G15 should be Sunday, July 14). I've looked at it, but can't figure out how to fix it. Can someone help me troubleshoot this?

Thanks you very much

That'll only change the date to/from Saturday/Sunday. The formula in G4 is an attempt to make sure the engineers don't work two Sat or Sun in a row. Since that formula looks two cells up, it won't work in G3.