Diagnosis
A non-unique index on reverse foreign key attributes is missing orincorrect.

Procedure
For all fields used in the binding of reverse foreign key associations anon-unique index needs to be defined in the database table (if usingdefault DACs).
Example: An attribute binding exists for an association from node A to adifferent node B, where node B is not directly situated under node A.Then an index for database table of node B would be needed with the keyfield of node A.