I`m not 100% sure if I`m right, but as I see it, it can be the
oil pump sealing ring in your pic 1111 647 9001,
gasket between the cranckcase halves 1111 029 0501
maybe someone other chimes in and can say you more.
The oil pump shouldn't leak into the crankcase if the o rings are blown. It'll leak everywhere else though.
I suspect you have a case gasket problem or loose case bolts. If the bar oil is leaking heavily on a leaky crank seal then I suppose it could vacuum some in, but a seal that loose would likely prevent the saw from ever running.
The part you need is dependent upon your serial number as shown on the ipl page I posted a picture of. After the serial number noted in the photo you need #9, before that serial number you need #10.
Your dealer likely has the latest ipl which only shows the later changes I don’t know why Stihl does this but the old paper pile show the changes much better and had previous part numbers also
Please see the edit in the last line of my last post I believe you have#10
Edit
The one with the foot (9)actually sat above the roll pin iirc. The solid one(10), the pin goes through the rubber ring.
Somehow I'm trying to remember another seal in there that isn't pictured in the ipl. But I'm probably just mixed up with another model. I have one that's pretty stripped down, so I'll have a look to figure out why I said that.View attachment 150086 I beg to differ on this. The Oiler shaft goes into the crank case behind the oil seal the oils seal actually seals on the Oiler worm gear on these saws and the o ring #6 is known for leaking on these pump shafts mine did it as well. There is a Viton oring available, dimensions are 7mmx1.5mm can get at MOST parts stores.
The larger rubber sealing ring #9 or #10 can be found online as well please check your machine serial number per the ipl page pictured as it will show you which one to get. The o rings #1 and #2 should also be replaced at the same time.