When there are two raml-module-builder based modules (e.g. mod-users and inventory-storage) which declare support for the Tenant API. The activation of the second module for the same tenant fails with the following response (from a POST to /_/tenant on that module):
This is due to a check for the existence of a PostgreSQL schema (https://github.com/folio-org/raml-module-builder/blob/d9100f6814e6223d54cfc720c02d2754976fbfd0/domain-models-runtime/src/main/java/org/folio/rest/impl/TenantAPI.java#L94) which is used to determine if a tenant has been initialised already. As modules currently share a schema named after the Tenant API only the first module's database script will be executed.
I believe this has not manifested itself on the blackbox environment, as it uses separate databases (on the same server). It has been exacerbated when using embedded PostgreSQL, as although each modules tries to start it's own PostgreSQL server process, the second one fails (due to them using both using port 6000).