Photoshop 2020 (version 21.1.3) using 100% CPU on iMac running macOS 10.14.6

I am using CC 21.1.3 on iMac with running OS 10.14.6 w/64GB Ram. CC is constantly using 100% or more(!!) of CPU which delays all tool usage. I had this problem occasionally with CC before the current update but was able to fix by closing the program and rebooting the computer. Now, that doesn't help. I have LOTS of scratch disk room, I have closed all other programs except Activity Monitor. 

Any help appreciated.

Michael

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