iOS 13 - WkWebView BUG: audio stops when in background

I've an app that uses WkWebView to play audio from Soundcloud and Mixcloud by using their javascript widget, on iOS 13 Beta 6 the audio stops when the app is not in foreground, even when Audio is on in Background Modes.

When starting the playback this assertions is thrown:

Error acquiring assertion: <NSError: 0x282cf67c0; domain: RBSAssertionErrorDomain; code: 2; reason: "Required client entitlement is missing"> {
userInfo = {
  RBSAssertionAttribute = <RBSLegacyAttribute: 0x1592432e0; requestedReason: MediaPlayback; reason: MediaPlayback; flags: PreventTaskSuspend | PreventTaskThrottleDown | WantsForegroundResourcePriority>;
}

And after entering background state the following assertion is thrown and audio suspended:

Can't end BackgroundTask: no background task exists with identifier 13 (0xd), or it may have already been ended. Break in UIApplicationEndBackgroundTaskError() to debug. 
[ProcessSuspension] Background task expired while holding WebKit ProcessAssertion (isMainThread? 1).

This is not happening in iOS 12, where the audio plays normally when in background.