On relaying the packet on GW:BB-ab, since it has the AMT entry for Host:A-a, it executes address resolution and forwards the VIP packet to Net:B-a.
Since GW:B has the most recent AMT entry for Host:A-a, it executes correct address resolution and forwards the packet to Net:A-c.
A router may have also AMT entries for intermediate address resolution. AMT entries for intermediate address resolution may be lost without harm, because the home router of a migrating host always holds its AMT entry.