If an annotation type has a feature which range is a subtype of string (https://uima.apache.org/d/uimaj-3.0.0/references.html#ugr.ref.xml.component_descriptor.type_system.string_subtypes ) the usual feature assignments in e.g. CREATE calls do not work. They are not set due to the RutaStream::assignFeatureValue method not having an appropriate case for these range types.
In the JCas cover classes however, the features can be directly set with strings.
If not setting the feature value is not intended Ruta behavior, I attached a patch that might fix that issue. On my end, this works with all feature assignment methods.