I have had the same cycle happen to me - the iOS app becomes unstable and crashes soon after opening, repeatedly. In other instances it takes a bit longer.
My setup: iPhone XS Max / iOS 13.1.3 (same happened in 13.1.1 and 13.1.2). Also running iPad Pro with iPadOS 13.1.3 and it is very stable, no issues.
I tried deleting the app, restarted phone, and reinstall - no dice, still crashes.