Now that IOS 13.3.1 allows Web Apps to work I am able to use my app again. However, the display regularly freezes and will not refresh when I switch screens and I have to ‘kill’ the app to restart it. So there is obviously still an error somewhere. Unfortunately, this error does not show up when I debug the app using Chrome on the PC (which I have used for years)
Any ideas how I can find out what the error is ? Is there another debug tool available that will allow me to find it.
Do you have access to a Mac? If so, you can use Safari on the desktop to open a web inspector on the device.
Afraid not, dyed in the wool Windows user 
Try including my console.log hijacker… it’s pretty straight forward, you need a div to accept the console.log output and that can be on any page. After that, just include the debug.js in your app header and initialize it via the instructions. IF you have any code errors, those should get trapped by either the console.err or console.warn handlers. This isn’t fancy but really works well when debugging devices in the wild.