Elevated commands can fail via winrm under certain conditions like the machine name being changed. Detect this by checking for a known exit code combined with known output included within stderr. If found, attempt to re-execute the command using a machine prefixed username if possible.
Vagrant Core Plugins
These are plugins that ship with Vagrant. Vagrant core uses its own plugin system to power a lot of the core pieces that ship with Vagrant. Each plugin will have its own README which explains its specific role.