In a recent paper, we presented scenarios of long-time asymptotics for the solution of the focusing nonlinear Schrödinger equation with initial data approaching plane waves of the form A1eiϕ1e−2iB1x and A2eiϕ2e−2iB2x at minus and plus infinity, respectively. In the shock case B1<B2 some scenarios include sectors of genus 3, that is, sectors ξ1<ξ<ξ2, ξ≔x/t, where the leading term of the asymptotics is expressed in terms of hyperelliptic functions attached to a Riemann surface of genus 3. The present paper deals with the asymptotic analysis in a transition zone between two genus 3 sectors. The leading term is expressed in terms of elliptic functions attached to a Riemann surface of genus 1. A central step in the derivation is the construction of a local parametrix in a neighborhood of two merging branch points.