Illegal key (&1) specified for entity &2 when handling Custom Fields.
&1 - The unique identification of a record in the entity specified by &2
&2 - The entity the record was supposed to exist for
A function handling custom fields has been called with information specifying a record that does not exist in the specified entity.
Check that the unique identification specified on the calls to the functions handling custom fields identifies records that does actually exist in the specified entity.