At the position I was (apparently) supposed to park, my train was obstructing several switches. I doubt this is how I was supposed to park it.
I can also confirm that every single activity that involves arriving at Oxford Cross on the Yellow line platforms has the exact same issue, at least one of the trains on them has overshot into the tunnel and won't move. This is not a rare issue; it happens every single time. Sometimes it's one train, sometimes it's both.