Import from Gitlab.com to Gitlab CE failing

Hey,

Project Import from Gitlab.com into Gitlab CE (10.0.4) fails for our project.
The repo itself is imported but fails after the first issue is imported.

All other issues and merge request are not imported.

Sidekiq logs:

Does anyone know how we can debug what is causing the issue and how we can eventually get the projekt imported?

Thanks for any help