Vanishing of the residue Q-curvature at zero

Let ${\bf D}_N^{res}(\lambda)$ be the residue family operator of order $N$, and define the associated residue Q-curvature by

$${\bf Q}_N^{res}(0):={\bf D}_N^{res}(0)(1).$$

Vanishing conjecture for residue Q-curvatures. For every $N\ge 1$,

$${\bf Q}_N^{res}(0)={\bf D}_N^{res}(0)(1)=0.$$

The case $N=2$ is established immediately before the conjecture. The source describes the general assertion as open.