We have taken a very hard decision to disable Transmission in version 4.0.6 due to outstanding bug where announces are seen as failed and retried consequently against tracker, increasing load on it. You can follow the issue as reported on GitHub. Please note that this is unrelated to recent issue with libcurl crashes, this is a logical bug in how client handles announces to tracker.

We recommend you downgrade to 4.0.5 which does not exhibit this behavior.