Invisible wall across Blood River Massacre gate

I've just spoken to the gate guard, who gave me a key.

I used the key on the keyhole. nothing happened.

I clicked on the giant wooden bar which keeps the door closed, and it SNAPPED like a dry twig, and the doors opened. (strange, I would have thought the key would just make it slide out of the way. Why did I need a key if I could just snap the door lock?

I was unable to run across the threshold, I hit an invisible wall. Running along back and forth, the invisible wall completely barred my path out of the town

After a period, the doors close by themselves, and I got "pushed" through the invisible wall onto the bridge outside the gates.

The doors kinda automatically re-opened themselves.

I am now unable to run across back the threshold back into the town, I'm hitting the same invisible wall that I was previously on the far side of.

 

The same thing just happened at the elf camp in Highvale outskirts. The gate was open, but I couldn't run through it. The game was showing the gates open, but it was as if the gates were closed. In exactly the same way as in Blood River, as soon as the big log gates closed, I was pushed over the invisible barrier and could run away.