When performing a content model document import either via drush or hook_update, an existing content model document will not get updated and a new one will be created if you leave off the leading slash
example:
`drush content-model-documentation:import /admin/structure/types/manage/centralized_content/document` will update an existing if there is one
`drush content-model-documentation:import admin/structure/types/manage/centralized_content/document` will always create a duplicate and make repeated aliases and cause general mayhem.
This is caused by the alias lookup failing to find `admin/structure/types/manage/centralized_content/document` because aliases all begin with a leading slash.
Make the lookup prepend the leading slash if none exists.
Fixed
1.0
Content model document
Crediting majorrobot for helping debug this issue and bring it to light.
This issue has been fixed. CM Document import is now works the same whether a leading slash is used or not.