DevTools failed to load SourceMap: Could not load content for file:///android_asset/www/js/app.18deb612.js.map: System error: net::ERR_FILE_NOT_FOUND code example

Example: DevTools failed to load SourceMap: Could not load content for

Open Developer Tools, 
go to "Settings" for Developer Tools, 
then uncheck Enable JavaScript Sourcemaps under the "Sources" settings.
Restart Browser if needed