I have the same issue and I didn't realize you can just modify and apply to fix it. What I was used to do is, go to settings and disable the docker and re-enable it. This might help with your 7+ containers. I only have issues with one container that requires br0 accesses.
you could always run a docker container designed to max out your cpu. Such as https://hub.docker.com/r/progrium/stress/
Log in to unraid using ssh
then just type
docker run --rm -it progrium/stress --cpu 10 --io 1 --vm 2 --vm-bytes 128M --timeout 100s