How to force iphone and ipad to eject when they can't sync

I have my iPad and iPhone in the sidebar of my MacBook Pro.

MacBook Pro is running OS X Big Sur 11.3.1

iPhone is running iOS 14.7..1

iPad is running iOS 14.7.1.

Sometimes the fan starts running, and the battery says the Finder is using significant energy. When I look at the sidebar, the iPad and iPhone are trying to sync unsuccessfully and are stuck.

• Trying to cancel the sync doesn't work.

• Trying to eject the devices from the sidebar doesn't work.

• Trying to right-click and force eject the devices doesn't work.

• Connecting an Apple cable to either device while the sync is stuck doesn't unstick it.

• Trying to log off the account fails because a sync is in progress.

• Trying to shut down the machine fails because a sync is in progress.

The only way to stop the sync is to force a reboot of the Mac.

And that's good a few days until the sync gets stuck again.