oil sticking to coolant bottle

[Macholmes07]

Recently changed oil cooler on my 2015 s3 along with the seal

(I did accidentally snap a bolt putting the cooler back on)

But still getting oil coming up to the expansion tank what could it be 🤔🤔

Have been told my waterpump/ thermostat is leaking, could it be this also?

 

Audi have said its unlikely the headgasket as the ea888 is a pretty bulletproof engine