The first thing I would do is test your iOS and Android builds in Dev/QA and make sure that all the events you are tracking are in fact firing correctly and consistently.
If you aren't already using it, you should have Griffon / AEP Assurance integrated into your apps so that you can test them in real time.
https://aep-sdks.gitbook.io/docs/foundation-extensions/adobe-experience-platform-assurance
This is much easier to use than setting up a proxy connection and testing with Charles or Fiddler or some other HTTP Sniffer program.
It almost sounds like Android isn't triggering properly all the time... but the only way to confirm that is to watch it in action.