sonofdbn

I tried deleting and then recreating proxynet, but that didn't help. Then I tried creating a new network, proxynet2. I assigned my Swag and Nextcloud containers to it and they seemed to be OK. Then I reassigned the containers back to proxynet and lo and behold, they're now working.
 
To tidy up I deleted proxynet2. So far, so good.
 
If things run fine for a few days, I'll mark this as solved.

So I did a little test: stopped docker containers and VM. Set the graphics card in the VM to the Nvidia card (no VFIO binding) and then booted up the VM.
 
It seemed to be running but I couldn't connect via RDP. So I thought about stopping the Nvidia plug-in. At that point I thought it might be a good idea to see what the the Nvidia plug-in is meant to do, and went to the support thread. I didn't understand everything, but in the first post there was this warning:
 
"Please be sure to never use one card for a VM and also in docker containers (your server will hard lock if it's used in a VM and then something wants to use it in a Container)."
 
Looks like my idea is horribly risky, so I've abandoned it.

Problem solved here:
 
 
Essentially the problem is an issue with libtorrent 2.x, which is used by qbittorrent, which I was running. Solution was to roll back to an earlier version of qbittorrent. See details in the quoted thread.