Now this is no longer possible I'm afraid, due to some change a bull can no longer do his thing when a cow is inside a gate. Pure discrimination against bulls with a roundpole gate fetish if you ask me. We cannot support racism here can we?
Picture of the setup:

As you can see, the cow is stuck in the gate, it can't move (much) but I can reach it with a bucket for milking without having to open the gate. If there is someone out there who's still getting this to work, are you orienting your gates to open towards the north instead of the east like in my pen? I changed the direction of my gates and shortly after that it stopped working.