Synchronization error

I'm sometimes getting a synchronization error if I decline an event:

RequestType: POST
RequestUrl: https://graph.microsoft.com/v1.0/me/events/AAMkADhmMjM5ZmVmLWZiNTgtNDcwMi05ZTU3LWZjOTJiNzI4OGVmNgFRAAgI3OmHplHAAEYAAAAAhddX0hORW0ir00tBC71axAcAlFbnrSgN8kiFXAX0LYvuUAAAAAABDQAA72K-L9WTT0mM70fgBnp9mAAGWi5eKAAAEA%3D%3D/decline
RequestData: {"sendResponse":true}
ResponseData: {"error":{"code":"ErrorInvalidRequest","message":"Your request can't be completed. The meeting organizer hasn't requested a response."}}