Error iOS App shows html code : Failed to load resource: the server responded with a status of 403

Ionic iOS app works fine but if it is in background for longer duration and then if we open it then html code is getting displayed because of below error.
Failed to load resource: the server responded with a status of 403 (Forbidden) http://localhost:8080/www/build/main.css

Config.xml is as below
content src=“http://localhost:8080

If we then close and open app again then all is fine now issues.