Failed to connect to instance

After finishing Act 1 I clicked on the traveling dialogue option and the game was loading Vastiri Outskirts.
Then I got an error "Failed to connect to instance".
Since then I can login, but as soon as I try to play my character, the loading of Vastiri Outskirts starts and I get the same error message.

I tried switching the Server from Frankfurt to Milan. Unfortunately this didn't change anything. Also loading another character in between didn't help.

I got the same error already while playing before, but in that case I was able to go to a new instance with the shortcut.
This time I can't select the waypoint or portal to use the shortcut. The game directly loads the broken instance and fails to load.

After some minutes waiting (probably instance timeout) it worked again.