An example of a non acyclic Koszul complex of a module

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In his paper "Residues of a Pfaff system relative to an invariant subscheme" in Trans. Amer. Math. Soc. 352, 2000, 4019-4035, F. Sancho de Salas defines the universal Koszul complex of a module M over a sheaf of rings O as Kos(M)=Λ(M)⊗ₒS(M), where Λ(M) and S(M) stand for the exterior and symmetric algebras of M, endowed with the usual differential, and he conjectures (Conjecture 2.3.) that Kos(M) is always acyclic. We give here an example of a non acyclic Koszul complex Kos(M).