Corrigendum and addendum to “Moduli spaces of framed symplectic and orthogonal bundles on P2 and the K-theoretic Nekrasov partition functions” [J. Geom. Phys. 106 (2016) 284-304]

We give a scheme-theoretic description of μ−1(0) and μ−1(0)//Sp(2), where μ is the moment map defining the space of ADHM data associated to framed SO(3,R)-instantons with instanton number 1. The irreducible component in μ−1(0)//Sp(2), other than the Zariski closure of the instanton moduli space, is non-reduced, which is a corrigendum to [Choy (2016), Theorem 4.3]. We further describe this component using the factorization property Braverman et al. (2006).