This bug may be caused by many different things.Maybe your global packages are corrupted in some way, I suggest doing the following.
1 Install Node Version Manager (or NVM for Windows) and install Node version 10.16.1. This is enough for angular 9 and from my experience, it is the most stable version for development. This should also change your NPM version so that may also help.
2 Uninstall global angular package npm uninstall -g @angular/cli
3 Force clear cache npm cache clean --force
4 You can also try clearing your %temp% and %roaming% AppData/npm-cache
5 install latest angular package npm install -g @angular/cli@<your-version>
6 if this error still occurs, consider using another shell.