DevTools failed to load SourceMap: Could not load content for bootstrap.min.css.map

CSS
Delete /*# sourceMappingURL=bootstrap.min.css.map */ in css/bootstrap.min.css
and delete /*# sourceMappingURL=bootstrap.css.map */ in css/bootstrap.css

It is working for me.
I hope it will work for you also.
Namaste _/\_
Source

Also in CSS: