I have a local block with a set of properties, one of them is a ContentArea. I have decorated this property with [DefaultDragAndDropTarget]. I render the local block with the EPiServer Property control. But when I drag n' drop a block to the property, I'm getting this error:
ContentReference: Input string was not in a correct format.
If I open up the fly-out where you can see all the properties in the local block, I can see that the block was added to the correct property. But if I reload the page or saves it, the block is removed from the property.
This is a confirmed bug. Bug #117952.
As of version 9.6 this finally works!