When there are multiple activities and activity is using external XSD file for schema reference, if there are multiple schema file defines the schema with different content but with the same element name, the BusinessStudio would load only one schema. This would cause some of the activity fail with input configuration error at design time. 

For example:
ActivityA is using schema file A.xsd which defines element MySchema with 3 children. 
ActivityB is using schema file B.xsd which defines element MySchema with 5 children. 

When launch this custom plugin in a child BusinessStudio, the BusinessStudio would only load MySchema once. That means both ActivityA and ActivityB would have the same input, and one of the activity would trigger a design time error:
Activity Configuration error. The activity [name] has input configuration error. Cannot load the schema for the element.
 

Activity Configuration error. The activity [name] has input configuration error. Cannot load the schema for the element

All Supported Systems

Make sure each element is unique in the schema files if using multiple schema files for different activity.