With the newest version installed, I started using a brush I have used many times before. If I switch to another tool then go back to the brush it frequently stops painting. It moves around the screen as a blank but no color is produced. The only way I have been able to stop this is to restart PS. Sometimes this does not work and I have to reboot the computer. IN 2019, this might happen every few weeks. Yesterday with 2020 it happened at least five times during a four hour session. The stamp tool works fine.