To reproduce, create a provisioning template with default flag set to true, let's say it's id is 1. Then try to create a new organization (would fail for location as well) like this

Organization.create :name => 'aaa', :provisioning_template_ids => [1]

it fails with blank .errors but if you check taxable_taxonomies object you realize that there's twice the same record (one from default, one from manual assignment) and last one's error messages contains cryptic error "Validation failed: Taxonomy has already been taken"

To test from hammer you can run following command

hammer organization create --provisioning-template-ids 1 --name test

this will return 500 and Foreman log contains not very helpful message

Action failed
 | RuntimeError: resource have no errors