AJAX error when configuring Panels

When configuring Panels panes and given the option to "Enter the title or NID of a node"

a) when adding content to a Panels pane:
Content > (pane cog icon) > Add content > Existing node > Enter the title or NID of a node
or
b) when pulling in Panels context:
Context > Add context (Node) > Enter the title or NID of a node

Entering a node title plainly, i.e. WITHOUT the ' [id: #]' results in an AJAX error when submitting the form.

An AJAX HTTP error occurred.
HTTP Result Code: 500
Debugging information follows.
Path: /ctools/context/ajax/configure/...
StatusText: Service unavailable (with message)
ResponseText: EntityMalformedException: Missing bundle property on entity of type node. in entity_extract_ids() (line 7501 of /.../includes/common.inc).

This can be reproduced by NOT selecting an auto-complete result, which would otherwise append the ' [id: #]' for you.