Uodates suddenly not downloading and installing

After a dozen of earlier updates inside system of Ubuntu Phone on Nexus 4 I suddenly discovered that my device is not updating anymore. It's still telling me that there are updates (it started with 2 new updates waiting a week ago and now already 19 waiting).
So Wifi and internet connections work fine.

Output of sudo apt-get update:

some repeating messages like:

W: Ophalen van http://ports.ubuntu.com/ubuntu-ports/dists/utopic/restricted/binary-armhf/Packages is mislukt 404 Not Found [IP: 91.189.88.140 80]

and then once:

E: Some index files failed to download. They have been ignored, or old ones used instead.
W: Er wordt geen vergrendeling gebruikt voor het alleen-lezen-vergrendelingsbestand /var/lib/dpkg/lock

Any help?

I think your /etc/apt/sources.list has the wrong url for the repository. Please post this file and/or try removing I think, the trailing /ubuntu-ports part from the url.