In Google Analytics under Acquisition -> Channels -> Referrals I observe tpc.googlesyndication popping up as a referrer.
Googles documentation suggests that clicks on doubleclick ads cause this referrer to pop up. By activating auto tagging traffic should be correctly assigned to the display channel. However, auto tagging is already active and working (the gclid parameter is not omitted).
Also, when adding landing page as a secondary dimension to the tpc.googlesyndication hits, it lists my own homepage as the main referring source (I know this is my own homepage since other landing page paths are specific to my pages URL structure).
If that was true, I would expect Doublclick ads on my own homepage to referr to itself. Does anybody else encountered a similar problem and/or has a possible explanation?