Dear Samsung Member,
Greetings from Samsung Customer Support!
Kindly perform the below steps to resolve issue:
Clear cache and data of Calender:- Settings > Apps > Menu (Three dots) > Show system apps > Search Calender > Storage > Clear cache.
If issue still persist, kindly send us log file through error report section from Samsung Member within 15 minutes of issue occurrence, this will help us to assist you better. (Samsung member > Get help > Send feedback > Error report > Select the issue).
Thank you for writing to Samsung.
Samsung Customer Support