I uploaded a 8.8 contrib image where each VirtualBox is defined as type 82540EM (intel e1000) can you check it if that fixes the problem for you ?
the box is available at https://atlas.hashicorp.com/debian/boxes/sandbox/versions/8.8 I did a cycle of 10 vagrant up / vagrant destroy and could not bring up a case where the changed ordering of Nics would prevent the nat network to be properly configured
