Can you please share the crash report with us. You can enable this capability on your iOS device, run the app and as soon as it crashes again, crash information with be shared with us. You can disable this capability afterwards.
Apple can’t provide crash reports if users don’t share the crash data with app developers. If a user reports a crash and you don’t have a corresponding crash report, ask the user to share the crash data with app developers.
Give these instruction to users. On all platforms, the crash data option is in the Diagnostics section of the Privacy settings.