Vagrantプラグインの更新失敗を処理する方法は？

今：

$ vagrant plugin update
Updating installed plugins...
Fetching public_suffix-3.1.1.gem
Fetching vagrant-lxd-0.4.2.gem
Traceback (most recent call last):
    19: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/bin/vagrant:182:in `<main>'
    18: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/lib/vagrant/environment.rb:290:in `cli'
    17: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/lib/vagrant/cli.rb:66:in `execute'
    16: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/plugins/commands/plugin/command/root.rb:66:in `execute'
    15: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/plugins/commands/plugin/command/update.rb:28:in `execute'
    14: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/plugins/commands/plugin/command/base.rb:14:in `action'
    13: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/lib/vagrant/action/runner.rb:102:in `run'
    12: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/lib/vagrant/util/busy.rb:19:in `busy'
    11: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/lib/vagrant/action/runner.rb:102:in `block in run'
    10: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/lib/vagrant/action/builder.rb:116:in `call'
     9: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/lib/vagrant/action/warden.rb:50:in `call'
     8: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/lib/vagrant/action/builtin/before_trigger.rb:23:in `call'
     7: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/lib/vagrant/action/warden.rb:50:in `call'
     6: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/plugins/commands/plugin/action/update_gems.rb:23:in `call'
     5: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/lib/vagrant/plugin/manager.rb:228:in `update_plugins'
     4: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/lib/vagrant/bundler.rb:242:in `clean'
     3: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/lib/vagrant/bundler.rb:242:in `each'
     2: from /opt/vagrant/embedded/gems/gems/vagrant-2.2.5/lib/vagrant/bundler.rb:251:in `block in clean'
     1: from /usr/lib/ruby/2.6.0/rubygems/uninstaller.rb:162:in `uninstall_gem'
/usr/lib/ruby/2.6.0/rubygems/uninstaller.rb:264:in `remove': uninitialized constant Gem::RDoc (NameError)

Vagrantでプラグインを更新するたびに、このエラーまたは同様のエラーが発生しているようです。私のシステムに問題がありますか？