wabenze,

If your car is a W 124 300TDT than it should have both tubings ridgid. On my car they are and the electronic parts catalogue confirms that to. If it is an other type ( W123 or 210 ) I don't know.
If it was a MB-stealer who did this evil to your car, ask him to show you on his EPC this "original" flexible hose ! That would exclude every discussion, wouldn't it ?
Good luck !

Danny