Random network instability/DNS issues

On my OMV server, I have SabNZBD installed via Docker to download from the usenet. Randomly, I will notice that my download speed will drop from the normal range (around 75-90MB/s) to a much lower speed (often <5MB/s). It is usually accompanied by messages that a handshake to one of my configured usenet servers has timed out (screenshot below). Also, when this situation occurs, it is sometimes, but not always, accompanied by DNS failures (trying to ping google.com will fail, for example).

My network interface was previously set up as a bridge (needed for a Docker container I no longer use), but today I used omv-firstaid to set it back to a regular ethernet interface, and the problem has persisted. The details are below. It is set to use my Unifi Dream Machine for DNS, which in turn points to my self-hosted Ad-Guard instance (on a separate device, not the same physical machine as OMV). I have previously changed this to use Google or Cloudflare DNS, but the problem was not resolved, so I changed it back again.

When this occurs, if I reboot OMV, the problem is immediately resolved and the same files will begin downloading at the normal speeds, and all the handshake errors are resolved.

Any idea where to begin troubleshooting?

Quote from hmoff

Are there any relevant messages in the kernel log? From a terminal (ssh) run dmesg.

I'm a bit of a noob, not really sure what I am looking for. Lots of messages about devices being renamed, entering different states and leaving promiscuous mode.

It's quite a bit longer than I initially thought, too long to post here, actually.

The slowdowns just started, here is everything in the log after what was already posted: https://pastebin.com/UXNbfu14

Quote from hmoff

OK, nothing interesting in there unfortunately. It's just full of virtual interfaces going up and down which is all due to starting and stopping Docker containers usually. It's a general linux issue not OMV specific from what I see so you might be better off asking in a general linux questions Reddit for example.

I was thinking that maybe it is something Docker-specific, because the last few times I have experienced my speeds coming to a halt, I could still ping, so DNS seemed to not be affected. Since my download utility is running in a container, and I haven't verified download speeds any other way, maybe it's only affecting Docker (or even that one container specifically).

Quote from jata1

I am not seeing this issue with speed but I have seen quite a few issues with DNS not resolving inside my docker containers. This has been happening for a couple of months and I couldn't work out what had changed.

It turned out that the issue was related to adguard and DNS rate limits together with some change made with docker DNS. I fixed the issue by setting adguard to have no DNS rate limit.

That's very interesting. I could see how downloading through Usenet could bump into that limit very easily, as there are multiple connections to multiple download servers all running concurrently. I just made that change and will keep my fingers crossed, thanks for the suggestion.