Busy BTT and airportd processes after macOS Big Sur 11.6.1 update

I updated to macOS Big Sur 11.6.1 this morning on an iMac Pro.

Since then, there have been a few times when I observe Better Touch Tool and airportd both burning 80-90% CPU. If I pick "Restart BetterTouchTool" from the menu, both processes fall down to negligible CPU use again.

Has anyone observed anything similar, and have you got a guess as to what might be going wrong?

If it matters, I have wifi active, but not logged into any wifi network. I do this because I'm on a wired network, but some applications such as Apple Maps complain if wifi is disabled. They rely on wifi for accurate positioning.