Diagnosis: Faulty switch
Treatment Plan: Fix for free
See, what happens is, when you push the switch down to unlock the windows the button is held down to make a new contact by a wire hitting plastic, looky.
But, what happens is, instead of the plastic piece looking like this,
That plastic wedge that holds down the button breaks off, like this,(pardon the B&W, it was the best contrast)
So now we have a switch that won't stay down, ergo, won't activate the back windows. The fix is to take the switch out and look on the bottom of it.
Now what you do here, is real tough....
Guess what, you just fixed it,
Only problem here is the switch doesn't raise itself when you want to child lock the back windows, so careful all you mamas and papas. Also, I would try and find the renegade plastic nib floating around, most likely it's stuck in some grease real close to where it's supposed to be. I'm going to stick some double sided tape and put something on it so I can raise lower it easier. Works like it should.
For anyone interested in "glueing" the part back in, let me know how it goes for you, I think the plastic is POM, you can read about it here, my best idea for the adhesive is loctite, partcularly this kind
How to take it apart.....
these little plastic tabs on the side hold in the defective piece, how many times did you crack the plastic getting this far?