Mediation Settlement Agreement

Mediation was not court orderd, too large for Small Claims Court, took place in Oregon. Agreement reached for partial amount of note balance due; owing party failed to sign agreement until almost 18 months after other party died and still it is undated. Agreement has become part of estate, but wondering if it is even valid since only the note holder had signed and dated the agreement. Can the heirs sue owing party for full amount of note balance since they believe the agreement is now a moot point?