PWA converted to APK shows address bar after x amount of time

I have set up our website to work as a PWA, i converted it using a PWA2APK converter, and installed it on my phone.

The manifest.json setting for display is set to standalone, and everything is working as expected, except once thing:

After an unclear amount of time, for a reason I have yet to figure out, it seems the display setting gets changed to minimal-UI.

Meaning, after leaving the app open in the background for a while - usually I see this when I open the app after it has been in the background overnight, the app refreshes, and then a top navigation bar is shown (such as you would see if you would set the display setting to minimual-UI).

I have not figured out how to even reproduce this issue, I tried disconnecting the internet, leaving it open and checking it again, but nothing I do seems to replicate the issue, it only happens when I am not trying to make it happen.

Any thoughts?
Thanks!

Still a mystery this one.

I connected the phone to the browser and opened the dev tool so that I will be able to see the console, my theory (hope) was that maybe what ever is causing this issue will show a clue in the console window, but while it was connected the issue did not occur.

Any thoughts or directions would help a lot!