fwiw- an easy and cheeeeeep dyi 500e/e500 maintence tip for ya:

>ordered rubber 'O-rings' seals for the dip stick from FastLane 10 of them for a grand total $1.60 -must order in groups of 10, per Phil- - (ordered oil filters for the E500 and ditto E320 Coupe too)

prior to r/r, the E500's dip stick wouldn't have a 'snap' stop when fully inserted into the (oil level check) tube- aka - not really sealed properly

after the 15 second r/r (remove old seal from the top of the dip stick and roll new one into its slot)- - viola! a nice firm snappy seal upon (dip stick) full insertion (into the tube)!'

Happy days! ...appears heat/use shrinks that little black rubber o-ring seal over time.

best regards
-fad