When updating packages on Anaconda-Navigator (AN) and you encounter unable to write packages to /Users/mb/opt/anaconda3/pkgs/cache/53d7ef51.json.
The solution provided by AN is to run sudo chown 501:20 /Users/mb/opt/anaconda3/pkgs/cache/53d7ef51.json in your terminal. Sometimes this also does not fix the problem.
I would suggest
Cd into /users/mb/opt/
Run, sudo chown -R 501:20 anaconda3/
sudo chown -R 501:20 /Users/mb/opt/anaconda3/
This should solve any future issues with read/write packages with AN.
Hope this works.