@Mango I have iOS version 18.3.1 on my iPhone14 / Suunto App 2.41.0 and no crash issue. Can you update your iOS and let us know if the problem persists? Second option is to install Suunto App beta version: https://testflight.apple.com/join/DJyDC5SU?fbclid=IwAR3jTWlAkPOE4uL_3ehgsHHRV4SGRXAM9NCWEFH34_aMtwfu_Ac6WYzQOJ0 I hope this solves the issue.

@Stefan-Radtke yes, record your Zwift activity on your Suunto watch instead of importing the Zwift or corresponding Strava activity. That is anyway what the watch + app is designed to do and requires no 3rd party syncing solution All your fitness related data will then get properly handled without weird TSS and calorie estimates.