Touchbar controls appear blank
Since upgrade to Big Sur, touchbar controls for brightness/volume/Siri occasionally appear blank after waking from sleep (see 1st screenshot - blank area on right). Touchbar remains responsive - I can expand the blank area to show more controls, and switching apps shows different controls as expected - but the volume area stays blank. I can fix it by restarting or by editing touchbar contents to drag the default items back in, but the issue recurs after a while.
After restoring default controls, touchbar is normal again - see next screenshot for comparison.
I do not recall seeing this happen while using Catalina or earlier versions of macOS.
MacBook Pro 15″, macOS 11.0