Hi everyone, recently I changed the Xenial box that KohaDevBox has configured. But it seems I didn't find (yet) the right box. I managed to have it working by upgrading to Virtualbox 5.1, and using the latest Vagrant from their site (1.8.7).
If you find a better packaged Xenial image, please let me know, or fill an issue to talk about it on KohaDevBox's github site.