This is because I have an early sample with an incomplete Factory partition. Should have mentioned that. Later devices are OK, but I don't have any so I can't share.
If you are still looking for Telenor Zyxel EX5700 I have one that is unused.
Price: £70 excluding shipping.
I live in Norway.
Sorry, seems I missed your message.
Meanwhile another router (ex5601-t1) has filled the need.
Hopefully someone else will get happy with your ex5700.