PersistentObjectConverter can't convert ValueObject
The PersistentObjectConverter can't convert ValueObject from an URL or something else, if they have the property uid.
In our use case we have a form that maps to an ValueObject. After handling the result we do a redirect back to the form providing the ValueObject as a parameter. The UriBuilder will create the url and attach the property uid to it.
Once extbase tries to map the parameters back to the ValueObject he find the property uid and can't set it to the target because there is no setUid.
One idea would be to add an TransientObjectConverter that will extend the existing PersistentObjectConverter and overwrite canConvertFrom and getSourceChildPropertiesToBeConverted.
As Mathias Brodala told me in Slack, we should check Flow and keep the sync. As I'm not that into Flow I could not say whether __identity is the same there as uid in CMS.
Affected are all versions above 4.7 incl.