App screens gone crazy since move to WKWebView - help needed

Since I moved from PhoneGap Build to VoltBuilder, which presumably uses WKWebView instead of UIWebView, my app screens have gone berserk. The splash screen does not appear, the only thing from the home screen that appears are the footer options and when I click on one of the options, the relevant screen appears in a tiny font and with all HTML visible, including the frames that are initially supposed to be hidden. I realise this is not a VoltBuilder issue, but can someone in the community with a successful iOS app please either help me out with whatever new command needs to be in config.xml to make this work or let me see a sample working app.
I have added the following into config.xml, but it hasn’t made any difference:

    <preference name="WKWebViewOnly" value="true" />
    <feature name="CDVWKWebViewEngine">
        <param name="ios-package" value="CDVWKWebViewEngine" />
    <preference name="CordovaWebViewEngine" value="CDVWKWebViewEngine" />

First thing to check is whether there are any error messages on the Safari Remote Console - anything there?

Yep, lots of errors due to access control checks and cross origin requests. But I thought I’d got rid of that issue with this content security policy in the section of index.html:
<meta http-equiv=“Content-Security-Policy” content=“default-src ‘self’”">
Looking further down at the errors, looks like Content-Security-Policy is wrong. e.g. next error line:
EvalError: Refused to evaluate a string as JavaScript because ‘unsafe-eval’ is not an allowed source of script in the following Content Security Policy directive: “default-src ‘self’”.
Function — kendo.all.min.js:26:442
getter — kendo.all.min.js:26:442
set — kendo.all.min.js:27:20797
(anonymous function) — index.js:222
Global Code — index.js:260
Function — kendo.all.min.js:26:442

OK, will go away and look at Cross origin, access control and Content Security Policy

Thanks for your help