What would cause the windows and turn signals to malfunction

I have never heard of this issue on this model but I'm going to assume there is some kind of short circuit going on. The window switch pack and turn signal combo switch are in completely different locations. You will need a qualified shop to do some electrical diagnosis. https://repairpal.com/repair-shops

Hello, Everything electronic in that vehicle runs through one of the signal acquisition(activation) modules (SAM). The SAM gets blamed for most issues in Mercedes Benz cars and SUV's, but that is because it is often the cause. Watch for other things to go wrong if the issue has not been fixed yet. Not only does the SAM act as a relay for electrical systems functionality, it also communicates digitally to other control modules on the vehicle.