環境
OS:Windows10pro1803
Vagrant version2.1.5
VirtualBoxのバージョン 5.2.18 r124319 (Qt5.6.2)
box:ubuntu/bionic64
Vagrantのプラグイン:vagrant-hostmanager(1.8.9 global)

新しくubuntu18.04の環境を作ろうとやってみたら起動時のSSH認証がうまくいってないようです。
初回起動は

Bringing machine 'default' up with 'virtualbox' provider...
==> default: Checking if box 'ubuntu/bionic64' is up to date...
==> default: A newer version of the box 'ubuntu/bionic64' for provider 'virtualbox' is
==> default: available! You currently have version '20181011.0.0'. The latest is version
==> default: '20181012.0.0'. Run `vagrant box update` to update.
==> default: Clearing any previously set forwarded ports...
==> default: Clearing any previously set network interfaces...
==> default: Preparing network interfaces based on configuration...
    default: Adapter 1: nat
    default: Adapter 2: hostonly
==> default: Forwarding ports...
    default: 80 (guest) => 8080 (host) (adapter 1)
    default: 22 (guest) => 2222 (host) (adapter 1)
==> default: Running 'pre-boot' VM customizations...
==> default: Booting VM...
==> default: Waiting for machine to boot. This may take a few minutes...
    default: SSH address: 127.0.0.1:2222
    default: SSH username: vagrant
    default: SSH auth method: private key
    default: Warning: Connection reset. Retrying...
    default: Warning: Connection aborted. Retrying...
    default: Warning: Connection reset. Retrying...
    default: Warning: Connection aborted. Retrying...
    default: Warning: Connection reset. Retrying...
    default: Warning: Connection aborted. Retrying...
    default: Warning: Connection reset. Retrying...
    default: Warning: Connection aborted. Retrying...
    default: Warning: Connection reset. Retrying...
    default: Warning: Connection aborted. Retrying...
    default: Warning: Connection reset. Retrying...
    default: Warning: Connection aborted. Retrying...
    default: Warning: Connection reset. Retrying...
    default: Warning: Connection aborted. Retrying...
    default: Warning: Connection reset. Retrying...
    default: Warning: Connection aborted. Retrying...
    default: Warning: Connection reset. Retrying...
    default: Warning: Connection aborted. Retrying...
    default:
    default: Vagrant insecure key detected. Vagrant will automatically replace
    default: this with a newly generated keypair for better security.
    default:
    default: Inserting generated public key within guest...
    default: Removing insecure key from the guest if it's present...
    default: Key inserted! Disconnecting and reconnecting using new SSH key...
==> default: Machine booted and ready!
==> default: Checking for guest additions in VM...
==> default: Setting hostname...
==> default: Configuring and enabling network interfaces...
==> default: Mounting shared folders...
    default: /vagrant => C:/Users/XXX/vagrant/ubuntu64_18
    default: /home/vagrant/workspace => C:/Users/XXX/vagrant/ubuntu64_18/workspace
==> default: [vagrant-hostmanager:guests] Updating hosts file on active guest virtual machines...
==> default: [vagrant-hostmanager:host] Updating hosts file on your workstation (password may be required)...
==> default: Machine already provisioned. Run `vagrant provision` or use the `--provision`
==> default: flag to force provisioning. Provisioners marked to run always will still run.

となります。
何やら新しい鍵のペアが作成されたようなのですがそれで一度vagrant haltしてから再度vagrant upしても

Bringing machine 'default' up with 'virtualbox' provider...
==> default: Checking if box 'ubuntu/bionic64' is up to date...
==> default: A newer version of the box 'ubuntu/bionic64' for provider 'virtualbox' is
==> default: available! You currently have version '20181011.0.0'. The latest is version
==> default: '20181012.0.0'. Run `vagrant box update` to update.
==> default: Clearing any previously set forwarded ports...
==> default: Clearing any previously set network interfaces...
==> default: Preparing network interfaces based on configuration...
    default: Adapter 1: nat
    default: Adapter 2: hostonly
==> default: Forwarding ports...
    default: 80 (guest) => 8080 (host) (adapter 1)
    default: 22 (guest) => 2222 (host) (adapter 1)
==> default: Running 'pre-boot' VM customizations...
==> default: Booting VM...
==> default: Waiting for machine to boot. This may take a few minutes...
    default: SSH address: 127.0.0.1:2222
    default: SSH username: vagrant
    default: SSH auth method: private key
    default: Warning: Connection reset. Retrying...
==> default: Machine booted and ready!
==> default: Checking for guest additions in VM...
==> default: Setting hostname...
==> default: Configuring and enabling network interfaces...
==> default: Mounting shared folders...
    default: /vagrant => C:/Users/XXX/vagrant/ubuntu64_18
    default: /home/vagrant/workspace => C:/Users/XXX/vagrant/ubuntu64_18/workspace
==> default: [vagrant-hostmanager:guests] Updating hosts file on active guest virtual machines...
==> default: [vagrant-hostmanager:host] Updating hosts file on your workstation (password may be required)...
==> default: Machine already provisioned. Run `vagrant provision` or use the `--provision`
==> default: flag to force provisioning. Provisioners marked to run always will still run.

となり何やら認証がうまく行っていないようです。
ただ起動はできているようでvagrant sshやRloginを使った時は問題なく入りました。
vagrant destroyしてみても結果は変わらずどうしたらいいのかわからない状態です。
一応動くことには動くのですが不安になったため質問しました。
以前作ったubuntu16.04の方では現在vagrant upしてもこのようなWarnigは出ておりません。