I’ve started using some progressive web apps more to listen to some audio streams. What I have observed is that the bug where the modem connection suddenly gets lost while still showing a mobile connection happens more frequently.
I can go all day most days without the bug, or maybe once during day, but when I use the PWA of Epiphany aka GNOME Web then the connection is lost within 30 minutes fairly consistently.
I think certain use cases lead to a pattern of network traffic that is much more likely to trigger that bug. Roughly like this I think: the delay between network packets happens to be close to the delay before USB runtime suspend happens for the modem.