Ampleness of non-symmetric line bundles on degenerations of abelian varieties

Answering a 1985 question of Moret-Bailly, we prove by way of counterexample that if a line bundle $\mathscr{L}$ on a degeneration of abelian varieties $G \to \mathrm{Spec}(R)$ is not symmetric, then $\mathscr{L}$ being ample on $G$ is not necessarily equivalent to $\mathscr{L}$ being ample on the g