IDE: Cannot paint entity around two fields

Summary:
Cannot paint an entity (inside another entity) around two (or more) fields.
(Works correctly around one field.)

Reproduction scenario:
1. On a Uniface Form, paint an entity.
2. Within that entity paint two fields.
3. Now try to paint another entity, within the first entity, around the two
fields.
4. Does not work: IDE gives error message:
[] User action failed to complete. Unexpected exception. [error=-100000]
Parameter pUriList requires value(s)

Actual Result:
Exception is thrown.

Expected Result:
Entity is created succesfully.