I'm using two schemas with no namespaces, which have the same element name.
When using both in the same process and choosing which one for a different activity this is not recognized and it's only detected one of them.
Despite both schemas are in the dependencies tab with different location names, it's only detected one of them in the activities. I also see this warning:

Warning:
Process import warning. The process [schemaswnonamespaces.module.Process] has imported multiple schemas with identical namespace [] and identical element name [PGT_-_Entity], but in different locations. This could inject ambiguity in the references made by activities and variables, please proceed to refactor whether element names, schema names or namespaces to avoid collisions. Alternatively you may remove the unnecessary imports from Dependencies section of the process.    

Schemas with no namespace and the same element creates ambiguity

All

The warning is valid and descriptive. Please modify your schemas as follow:

1- Add an unique namespace for each schema 
OR
2- Make the element name to be unique in each schema