They do indeed suffer from this but can't imagine 3 being like it ?
Try the back switches on the arm resty bit to see if any different for rear windows ?
If not it's a case of first take the switch out and probe to make sure you are getting output, you know you have a neg and pos there as one works.
The only thing that is common to all three is the switch, so could well be the SW but all three is a bit unusuall.
Itvis most likely to be the switch, can only imagine that previous owners never used these ones ?
tabetha
ps the switch is the same as any four lecky windy sierra so don't pay OTT prices !!