Maximum number of concurrent DNS queries reached and slow network

The issue I am facing:
I keep finding my pi hole has multiple incidents of the "Maximum number of concurrent DNS queries reached (max: 150)" error and I have noticed my network grind to a halt at times which seem to coincide when the Pi gets these errors. This I think is related to suffering buffering issues with Plex etc as it seems like something is swamping my network.

Details about my system:
My Pihole is installed on a Pi3 and has been running well for a good while.

What I have changed since installing Pi-hole:
I have also made a bit of a change to force safe search on google and bing but I can't quite remember how I went about it, I feel it was something to do with editing DNS records or something.....I've been trying to find the guide I used but I can't find it right now.

I think this was what I did to force safe search....I'm not 100% sure but I've got it bookmarked and it certainly rings a bell!

Please generate a debug log, upload it when prompted and post the token URL here.

Here's my debug log:

https://tricorder.pi-hole.net/C1U7d57J/

If it helps any, I get the same message as well occasionally. Unbound (the feature-rich dns resolver) has lots of documentation about this, and ways to configure Linux networking to allow more than 150 connections. This message is temporary for me, doesn't prevent long-term network use.

I haven't tried plex streaming, but respect the software and the idea of local content it promotes.

Is this local content or cloud streaming?

The Plex streaming is local media but I'm getting loads of buffering and slow network messages at times. It only tends to last a few minutes but it never used to do it.

I had the same problem after upgrading Pi-hole to the latest stable components which led me to believe that it was the upgrades fault.
Since I read something about "there have been kernel updates" in the terminal while upgrading I rebooted my RPi4 running Debian Bullseye (RaspberryPi OS) and it was then the problems started.
It looked much like the dreaded DNS loop but since I didn't make any changes, at least knowingly, to the rest of my setup, I ruled it out.
Then I saw in my routers device list that the RPi4 is connected both by ethernet and WiFi. I deactivated WiFi and everything is back to normal.
I suspect that some update to Debian led to activation of WiFi which before was blocked by rfkill. I didn't even recall that I had the RPi4 connected to WiFi before.
So maybe you should check this.

Interesting that you say this, I updated the Pihole yesterday and noticed a messaging saying wifi was blocked by rfkill, and so far today I've not noticed any issues nor had any errors thus far....

Edit.... famous last words.... immediately after posting that I went and checked my pihole and 2 more "Maximum number of concurrent DNS queries reached" have occurred today...

Tough luck!
Good luck solving your problem which most certainly isn't the same I had.

A few hours later now and I've got a handful more errors and trying to watch local media on Plex keeps buffering or failing.

My feeling is that something on my network is swamping it with traffic and causing me all kinds of network problems but I have no idea what. Not where to even start with diagnosing what the cause of the problem is.

Any help is much appreciated.

Turn off internet on any devices you aren't using. Saves network chatter. I have a tablet that has a domain or few (or about five or os) that slip through my devices firewall app. So I just disable network on it periodically--even when reading.

I thought I had got to the bottom of this issue when I paused all active files on a torrent client in my NAS but the other day I had network issues again and another bunch of Maximum number of concurrent DNS queries errors and having tried to watch a film earlier, I've suffered with terrible buffering again so I'm back to square one.

Is anyone able to have a look at the logs I uploaded to see if there are any clues in there?

Note that the uploaded debug logs are deleted after 48 hours, so you will need to run another debug command and post the new debug token here.

When you look at the Pi-hole's Dashboard are there any clues in the Top Domains and Top clients, showing what is being looked up, and what is doing the looking, so much?

Just uploaded a new log:

https://tricorder.pi-hole.net/1LMFJuE2/

As far as I can see, there's not anything looking really out of place in the top domains or clients lists.

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