High CPU usage on the host (Big Sur)

I’m getting 150% CPU usage on my host (MacOS 11.6.1) while the Ubuntu guest is idling. I see this issue in the VirtualBox forums, but everything runs fine if I start the VM directly from the VirtualBox app. It only happens when I start it from vagrant.

I tried the fixes found in the VirtualBox threads (disable audio, have vagrant start in gui mode, increase resources), but nothing has worked except starting from the VB app gui. (And then I lose all the vagrant functionality.)

Is there a fix?

VirtualBox 6.1.30
Vagrant 2.2.19
MacOS 11.6.1