YouTube video hangs with MacOS 27.0.1 on M1 iMac. Audio continues. Loss of control.

On my M1 iMac since upgrading to MacOS 27.0.1, while watching YouTube in Safari, the video often freezes, showing the beachball spinner. But YouTube audio continues. Keyboard and mouse fail to elicit responses. Must do hard reset (with long power button press) to regain control. What is going on? It is happening a few times a day, sometimes within minutes of a reboot.