Recently found under examination that sticking front heated seat switches as found in the 1986-1991 Mercedes Benz 560 series sedan and coupe could be related to a crack in the switch holder as shown in the photos.
If your switch is hanging, which means you click it and it hangs (this is very different from being completly hard to push and jammed) then it's a high probablilty you have some cracks in your swich holding bracket on the coin tray.
If you look at this photo you can see the fatigue in the plastic which results in cracks, I'd guess you could super glue these cracks (with the switches removed of course) and with some pressure to hold them together and your factory switch would be okay.
Keep in mind that I have come across MANY stuck window switches, but not too many if any power heated seat switches. This with $1 Mil MSRP of MBW126 under the belt in terms of = purchased in distress = scrap value.
At some point these cars will become rare, and I am offering up some information I have seen. Do with it what you will.