Surface density for a migrating planet with q = 3.6 × 10⁻⁴ shortly before the end of the simulation. The corresponding migration track is shown in the bottom panel of Fig. 4. The planet is strongly eccentric (e ≃ 0.05), which manifests itself via the eccentricity of the gap and the relative position of the planet with respect to gap edges. We point out that this unusual result (compared to our remaining simulations) might be caused by a numerical artefact.