PiHole has stopped blocking ads

PiHole has been working well for quite some time. Its running on a Debian system and using Apache.
DNS is configured correctly (I think) on the router, with fall back in case the server falls over.

However, I've noticed today that ads are getting through. I can't figure this out, I'm not running Ipv6, I've updated PiHole, have reloaded / restarted a few times and no change. Can access the webportal and not seeing anything odd there.

Here is the log:

Thanks for that, jfb.

Found the issue late last night, it seems that one of the applications on the laptop is acting as a DNS server. PiHole worked fine once it was turned off.

This raises quite a few other questions, but not for this forum, I think.