The window.applicationCache status is 2(Checking) when the issue occurs. I have some method called on the listener to some of the application cache change events. But when the issue occurs, I see none of the events getting fired. Request to Manifest is also stuck forever when I inspect the network tab. The device I am using is Ipad IOS-12.0.
In the success scenario, the status is 2(checking), then it raises noupdate event and subsequently the application cache status changes to 1(idle). This issue is intermittent and gets reproduced sometimes when I freshly launch the web app.
Since this feature is going to be deprecated by apple, the support hasn't come. you can do a workaround instead, have a listener on the checking event and may be after a setTimeout of 3-4 seconds you can perform your further calls.
Will keep this thread posted once an update comes.