We have been using parallel execution since it was added, but after upgrading to 2.0 we have been getting various non deterministic bugs, especially around dependency downloading.

After upgrading to 2.1 or the 2.2 release candidate this has gotten even worse, and we get many messages saying metadata is corrupt in snapshots, and our build is never able to finish correctly, often we have to delete the gradle cache entirely, as the downloaded dependencies are completely broken.

Sometimes we also have to delete the local .gradle directory in the project, as that too can become corrupt, beyond what clean will fix.