On the 123 there is a drain hole in the channel that the window seal sits in , if the water is flowing through the seal somewhere then it will leak out the drain hole. I'm not sure if the 126 is the same but you probably need a new seal to stop it. Good luck.
1985 380SE- 160,000km 'Blistu' - Sold
1988 300CE- Eva,my garage mistress
2007 R350 4matic- The Black Pearl
2011 Ford Ranger-Work truck
1974 25' Trojan Sea Raider- 'Grannyknot'
2002 215 cm Atomic DH skis- Canadian SDH record holder, 175.5km/h- Vars 2010