My Warzone crashes just when I am about to join a game. I have heard this happening with other people too, specifically after the season 2 update and on Xbox, I am on a Xbox Series S. And this only happens on Caldera matches, Rebirth Island works just fine.
I'm not sure if there is actually something you can do about it rather than the usual uninstall/reinstall suggestion that most of the times is not working...
Sounds like a game issue rather than an Xbox issue but i would suggest to download Xbox Insider Hub on your Xbox and submit a bug report just right after the crash. If you do that it will collect logs and submit them to help the Xbox team get valuable information to resolve the issue.
After installing the Xbox Insider Hub you can report the issue by holding the home button on the controller and selecting Report Issue.