Drag and Drop Permits Dropping Into Other Drag and Drop Instances

Steps to Reproduce

• Navigate to a node edit page that has multiple drag and drop field instances.
• Move an item from one drag and drop field into another field.
• Hit the save or preview button.

Expected Behavior

The drag and drop fields should have a mechanism that prevents dragging and dropping an item into a different field instance.

Actual Behavior

The drag and drop fields permits dragging an item into another field, and if the user attempts to hit the save or preview button, an error message appears at the top of the screen that says "The referenced entity (node XXXX) is invalid". No other errors were found on Drupal's or the server logs. Screenshot is attached.

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