Unfortunately, the common front engine leak is due to the retraction of the two sealing masses at the point of convergence between the block, the head, ant the upper/lower timing covers.
It usually soaks the alternator and air pump. If you have time, take it all apart and clean it up and watch it closely. You will find that the only way to tell whats leaking, if its in that area, is to replace the upper cover seals; and then, the head gasket and seals when it doesn't work. If you look at the new head gasket FROM Mercedes you will see inserts in the affected areas that would make one think that there is a difficiency in the original gaskets. I think they are receeding under the head which leaves a gap or reduced contact at that critical junction.
Bosch Master, ASE Master, L1
33 years MB technician