Dictionary with RelationLists as `value_type`

Hi all

I have got a behavior that extends the schema of a type with some fields. Now I want to add a field that is a dictionary and its value_type should be a RelationList.

    dictWithRelations = schema.Dict(title=u"Some Relations lists",
                                    required=False,
                                    key_type=schema.TextLine(title=_(u'afield')),
                                    value_type=relationfieldschema.RelationList(
                                       title=_(u'relations'),
                                       default=[],
                                       value_type=relationfieldschema.RelationChoice(
                                           source=CatalogSource(portal_type=['Document', 'Folder'])
                                       ),
                                       required=False,
                                    ))

After I have assigned this behavior to Documents I can create a Document and see my new field. I can add items to that field but if I try to add a relation the widget says "Loading failed". In my browsers development console I can see error 404 for this Url:

http://localhost:8082/Plone/de/++add++Document/++widget++form.widgets.IBehaveDifferent.dictWithRelations.0/@@getSource?query={"criteria"%3A[]%2C"sort_on"%3A"sortable_title"%2C"sort_order"%3A"ascending"}&attributes=["UID"%2C"Title"%2C"portal_type"%2C"path"%2C"getURL"%2C"getIcon"%2C"is_folderish"%2C"review_state"]&batch={"page"%3A1%2C"size"%3A10}&_=1461052944177

If I add a RelationList field to my behavior schema directly everything work as expected:

    relations = relationfieldschema.RelationList(title=_(u'relations'),
                                                 default=[],
                                                 value_type=relationfieldschema.RelationChoice(
                                                    source=CatalogSource(portal_type=['Document', 'Folder'])
                                                 ),
                                                 required=False,
                                                 )

I have tried changing source=CatalogSource(portal_type=['Document', 'Folder']) to vocabulary='plone.app.vocabularies.Catalog' as well. In this case the RelationList added directly to the schema works but the one in the dictionary does not work too. The error in browsers development console is:
select2.js:1800 Uncaught TypeError: Cannot read property 'length' of undefined http://localhost:8082/Plone/++plone++static/components/select2/select2.js

I hope someone can help or show the correct way to have a Dictionary with RelationLists.

Has anyone made any progress on this? I'm facing a very similar situation.
class IThreeFrameRun(IVeracisRunBase):

testiChipvocab = schema.Choice(
    title=_(u"Test Vocab"),
    description=_(u"Test Vocab"),
    required=False,
    source=IChipsAllVocabulary,
)

#works
aliquot_to_well = schema.Dict(
key_type=schema.TextLine(title=u"Aliquot ID"),
value_type=schema.Choice(source=IChipsAllVocabulary, required=False)
)
#gives "AttributeError: portal_catalog"

how can a JavaScript error be "very similar" to a Python one?

please open a different thread an provide proper information, starting with the whole traceback, if you want to be helped.