A generation of symbols asserted for $n \geq 0$ in the proof of Theorem 3.3 of the original paper in fact only holds for $ n > 0$, thus undermining the proof of the theorem. A new version of Section 3.5 of the original paper is given, culminating in a corrected proof of Theorem 3.3. The author thanks Deepak Khosla for pointing out the gap in the previous version of the proof.
"Erratum: A local proof of Petri's conjecture at the general curve." J. Differential Geom. 77 (1) 169 - 173, September 2007. https://doi.org/10.4310/jdg/1185550819