Github user dkuppitz commented on the issue:
https://github.com/apache/tinkerpop/pull/721
^
[solved](https://github.com/apache/tinkerpop/commit/a86097d0823397f0485566e8fd5def7a82fb32f3).
The `execute()` command was just missing a `waitFor()`, which sometimes led to
a missing or incomplete / corrupt zip file.---
