cross-database reference issue with collective.z3cform.datagridfield.registry.DictRow

[monroi]

I tried to use DictRow to set a registry record in on eof my packages. Worked great when I installed the package on the first site, but got the following error when I tried to install the same package on a different site that's on a different database (different ZODB mount points on the same "buildout")

Traceback (innermost last):
  Module ZPublisher.WSGIPublisher, line 161, in transaction_pubevents
  Module transaction._manager, line 252, in commit
  Module transaction._manager, line 131, in commit
  Module transaction._transaction, line 311, in commit
  Module transaction._compat, line 50, in reraise
  Module transaction._transaction, line 302, in commit
  Module transaction._transaction, line 447, in _commitResources
  Module transaction._compat, line 50, in reraise
  Module transaction._transaction, line 421, in _commitResources
  Module ZODB.Connection, line 497, in commit
  Module ZODB.Connection, line 546, in _commit
  Module ZODB.Connection, line 578, in _store_objects
  Module ZODB.serialize, line 430, in serialize
  Module ZODB.serialize, line 439, in _dump
  Module ZODB.serialize, line 348, in persistent_id
ZODB.POSException.InvalidObjectReference: ("Database 'db11' doesn't allow implicit cross-database references", <Connection at 7f0698393748>, <collective.z3cform.datagridfield.registry.DictRow object at 0x7f063c96a048 oid 0x433a43 in <Connection at `7f069a60ee80>>)

[monroi]

A little bit more information on how to reproduce the error.
The interface

from collective.z3cform.datagridfield import DataGridFieldFactory
from plone.autoform import directives

class IBreadcrumb(model.Schema):
    breadcrumb_title = schema.TextLine(title=_("Title"), required=True)
    breadcrumb_url = schema.TextLine(title=_("URL"), required=True)

class IMyInterface(model.Schema):
    directives.widget(breadcrumbs=DataGridFieldFactory)
    breadcrumbs = schema.List(
        title=_("Additional settings"),
        value_type=DictRow(title=_("Breadcrumb"), schema=IBreadcrumb),
        required=False)

and in the registry.xml file

<registry>
    <records interface="ims.pathbar.interfaces.ICustomPathBar" />
</registry>

Now in order to reproduce the error

1. Create two ZODB mount points in the ZMI. These databases must be configured to allow-implicit-cross-references=false
2. Create a Plone site in each.
3. Install the above profile on the first site
4. Install the above profile on the second site - this produces the error

Restarting the Zope client allows the profile to be installed on the second site. It is unclear why this would ever try to make a cross db reference between these two sites. Perhaps some RAM cache with PersistentField?