[plone.restapi] KeyError('@id')

During a large import using collective.exportimport, we have some errors like

WARNING:collective.exportimport.import_content:cannot deserialize http://nohost/eteaching/praxis/erfahrungsberichte/slidecasts-als-studienleistung-in-den-umweltwissenschaften/u-teach-fe-erstellen-von-elektronischen-lehreinheiten-durch-studierende-in-den-forst-und-umweltwissenschaften: KeyError('@id')

The error makes not much sense because the related JSON record contains an entry for @id. Any idea what the real problem could be?

'@id' is a read-only field that can not be set via plone.restapi AFAIK. Maybe c.exportimport tries to set that? Can you provide the actual plone.restapi request that is sent?