Few things to do to fix ng build --prod issues

Update packages:

npm install -g npm-check-updates

ncu -u 

Delete node_modules folder

npm install

Rollback webpack:

npm remove webpack

npm install webpack@3.11.0

Upgrade angular cli:

npm uninstall -g angular-cli  npm cache clean  npm install -g @angular/cli@latest

or downgrade bootstrap

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Feng