I have a Samsung Galaxy S20 Plus 5G and use an app called Talkatone to receive Wi-Fi calls from a friend in the USA. I have a very fast and stable Wi-Fi connection.
The app worked fine in January-March, but from April onwards the calls keep cutting out and it always seem to be at exactly the 16 minute mark. The app will just say 'call ended' as if someone has hung up even though neither of us did. I'm pretty sure it's an issue at my end and not my friend's, as he makes long calls to others with no issues.
I have an old Google Nexus 7 tablet so decided to install Talkatone on that, and the calls are working fine when I use that (which I assume also implies that the issue is not my internet connection). Naturally it's frustrating that such an old device is more reliable than an expensive modern smartphone.
I've tried deleting and reinstalling Talkatone to no avail, and I have the latest firmware update installed on my phone, so I'm out of ideas.