big slur os stops fans

The last update for Catalina (came out the same time big slur became available in software updates) stopped my MacBook Pro 2015 (A1398) from using the fans. The fans no longer turn on. Updating to big slur os continued the problem. Running diagnostics (turn off computer, hold down "D" key after reboot) turns on the fans and shows they do work. Diagnostics also says there is no problem. The fans only run during the diagnostics test. Once computer is rebooted fans do not turn on and computer becomes hot to the touch. I have to use a fan board underneath the computer to use it now.