Since I purchased my car my master window switch will roll down all my windows except for the rear drivers side window. I can roll down the rear drivers side window with the rear driver side door switch.

Any idea of what to check or what is the cause, I am confused by the window semi working.

 

It'll be a duff master switch that'll be causing that issue. Try squirt a bit of contact cleaner down the gap and see what that does. Otherwise go grab a replacement master switch. Trying to troubleshoot small PCBs like that is time consuming and sometimes fruitless.

 

If similar to LS400 then conductive rubber contacts.
One way to verify if the switch element is the cause is to jumper the appropriate wires to the offending window.motor. (wirhout jumpering wrong wires)

Any childproof setting to be aware of?

 

The child locks are not on and I took the switch apart and cleaned the contacts with rubbing alchol. Is it possible onw of the pins had a bullseye break and just needs to be soddered?