Anyone knows what this is, and why?
According to the web, Sentry is "a developer-first error tracking and performance monitoring platform that helps developers see what actually matters, solve quicker, and learn continuously about their applications" [1]. It "provides end-to-end distributed tracing, enabling developers to identify and debug performance issues and errors across their systems and services" [2].
There is more information: https://sentry.io/for/full-stack/
But traktor closed normally, and I never got this message before in all my years of traktor usage.