Yes, I completely understand this of course, especially in a situation where it is hard to reproduce.
For completeness I will state a few facts that seem to be clear:
1- Roon logs (which you enabled on my account) do not show any Roon error, just sudden death of the process. It seems to me this means iOS is somehow determining your process has violated some rules and kills it. This has been the case with ALL versions of iOS 13 (and I don’t do betas), so it seems like some new safeguard that started with this version of iOS.
2- The problem does not show up in iPadOS, which is pretty stable. And by and large it seems to me that no major OS core feature is different between iOS and iPadOS, so it seems to me that what is triggering the kill is something in the branch of the code in Roon app that pertains the iPhone.
3- The iPhone app is very stable until it reaches a point where it starts crashing ALL the time. It won’t stay up more than a minute in this state. So I am thinking there’s got to be some cache that is getting out of bounds, or something that is building up and then making it crash, and PERSISTS over sessions.
4- I have not identified what conditions make it come back to stable. It has not been deleting the app and reinstalling, and I don’t know if there are any caches that persist in that situation (I doubt it).
5- I don’t really have anything particularly strange I run on any of these devices. And I have plenty of memory - my iPad is an iPad Pro 10.5" with 512GB, and my iPhone an XS Max with 512GB also, both have ~100GB free, and both have very similar apps installed and usage patterns. And both have been updated to the latest iOS/iPadOS versions as they come out (no betas).
6- One more bit: the iPhone app has crashed on me without any interaction meaning I started it (after a crash), it was loading, and without me touching the screen at all it would suddenly crash. So it doesn’t seem to be something related to interactions and GUI per-se, but something related to whatever resources it is using from the OS that makes the OS decide to kill it.
Guys: I understand the complexity of troubleshooting issues like this, especially when they are related to some form of cross-session buildup. It is also my understanding Xcode cannot really maintain OS states across sessions which makes this particularly hard to troubleshoot.
However, I can also tell you I use many apps in iOS and iPadOS and none have ever had this kind of issues.
Have you contacted Apple for help?