I have noticed my dipstick moves up almost a 10mm when driving. I push it back in but it always pops up again. Recently I could have a look at a friends 1997 W210 E420 (E400 here in Japan) and noticed he doesn't have the hole that I have on the side of my dipstick tube about 10mm down. So this is why my dipstick doesn't want to remain closed. Any idea why there is a hole?
My car has only 50,000km on it, and I was planning to keep it for a long time, but I could get another one if I feel this one has been tampered with in a bad way.
Thank you for any ideas.

 

should be a rubber o-ring on the dipstick to keep the dipstick tight in the tube.