I have an application on TestFlight with some internal users, yesterday a user reported a crash via TestFlight, and the crash was not delivered to me, just the feedback.json file, it’s almost 24 hours and yet without the crash file.
TestFlight crashes are not delivered
Does the user that reported the crash have analytics shared with developers turned off? If so you won't get a crash file.
You can ask them to send you the file. You can get the file by going to settings > privacy > analytics > analytics data
You can ask them to send you the file. You can get the file by going to settings > privacy > analytics > analytics data