Ruby2.7.2→2.7.4アップデートでのwarning

前提・実現したいこと

lxcのコンテナで仮想環境を作り、Rubyのバージョン2.7.2から2.7.4へのアップデートができるか検証をしています。
アップデート自体は問題なく終了し、サーバーも起動した（はず）のですが、unicorn.logを確認してみると
以下のWarningが発生していました。
このサーバを起動する度に出てくるこのエラーを無くしたいです。

/home/---/.rbenv/versions/2.7.4/lib/ruby/2.7.0/json/version.rb:4: warning: already initialized constant JSON::VERSION
/home/---/.rbenv/versions/2.7.4/lib/ruby/gems/2.7.0/gems/json-1.8.6/lib/json/version.rb:3: warning: previous definition of VERSION was here
/home/---/.rbenv/versions/2.7.4/lib/ruby/2.7.0/json/version.rb:5: warning: already initialized constant JSON::VERSION_ARRAY
/home/---/.rbenv/versions/2.7.4/lib/ruby/gems/2.7.0/gems/json-1.8.6/lib/json/version.rb:4: warning: previous definition of VERSION_ARRAY was here
/home/---/.rbenv/versions/2.7.4/lib/ruby/2.7.0/json/version.rb:6: warning: already initialized constant JSON::VERSION_MAJOR
/home/---/.rbenv/versions/2.7.4/lib/ruby/gems/2.7.0/gems/json-1.8.6/lib/json/version.rb:5: warning: previous definition of VERSION_MAJOR was here
/home/---/.rbenv/versions/2.7.4/lib/ruby/2.7.0/json/version.rb:7: warning: already initialized constant JSON::VERSION_MINOR
/home/---/.rbenv/versions/2.7.4/lib/ruby/gems/2.7.0/gems/json-1.8.6/lib/json/version.rb:6: warning: previous definition of VERSION_MINOR was here
/home/---/.rbenv/versions/2.7.4/lib/ruby/2.7.0/json/version.rb:8: warning: already initialized constant JSON::VERSION_BUILD
/home/---/.rbenv/versions/2.7.4/lib/ruby/gems/2.7.0/gems/json-1.8.6/lib/json/version.rb:7: warning: previous definition of VERSION_BUILD was here
/home/---/.rbenv/versions/2.7.4/lib/ruby/2.7.0/json/common.rb:100: warning: already initialized constant JSON::NaN
/home/---/.rbenv/versions/2.7.4/lib/ruby/gems/2.7.0/gems/json-1.8.6/lib/json/common.rb:99: warning: previous definition of NaN was here
/home/---/.rbenv/versions/2.7.4/lib/ruby/2.7.0/json/common.rb:102: warning: already initialized constant JSON::Infinity
/home/---/.rbenv/versions/2.7.4/lib/ruby/gems/2.7.0/gems/json-1.8.6/lib/json/common.rb:101: warning: previous definition of Infinity was here
/home/---/.rbenv/versions/2.7.4/lib/ruby/2.7.0/json/common.rb:104: warning: already initialized constant JSON::MinusInfinity
/home/---/.rbenv/versions/2.7.4/lib/ruby/gems/2.7.0/gems/json-1.8.6/lib/json/common.rb:103: warning: previous definition of MinusInfinity was here
/home/---/.rbenv/versions/2.7.4/lib/ruby/2.7.0/json/common.rb:129: warning: already initialized constant JSON::Unparser Error
/home/---/.rbenv/versions/2.7.4/lib/ruby/gems/2.7.0/gems/json-1.8.6/lib/json/common.rb:128: warning: previous definition of UnparserError was here
I, [2021-08-17T02:55:08.323252 #16083]  INFO -- : listening on addr=0.0.0.0:3000 fd=7
I, [2021-08-17T02:55:08.332895 #16087]  INFO -- : worker=0 ready
I, [2021-08-17T02:55:08.334772 #16088]  INFO -- : worker=1 ready
I, [2021-08-17T02:55:08.336756 #16083]  INFO -- : master process ready
I, [2021-08-17T02:55:08.336929 #16090]  INFO -- : worker=2 ready
I, [2021-08-17T02:55:08.338726 #16092]  INFO -- : worker=3 ready
I, [2021-08-17T02:55:08.340373 #16093]  INFO -- : worker=4 ready
I, [2021-08-17T02:56:17.374186 #16083]  INFO -- : reaped #<Process::Status: pid 16092 exit 0> worker=3
I, [2021-08-17T02:56:17.374347 #16083]  INFO -- : reaped #<Process::Status: pid 16093 exit 0> worker=4
I, [2021-08-17T02:56:17.474896 #16083]  INFO -- : reaped #<Process::Status: pid 16087 exit 0> worker=0
I, [2021-08-17T02:56:17.475046 #16083]  INFO -- : reaped #<Process::Status: pid 16088 exit 0> worker=1
I, [2021-08-17T02:56:17.475109 #16083]  INFO -- : reaped #<Process::Status: pid 16090 exit 0> worker=2
I, [2021-08-17T02:56:17.475190 #16083]  INFO -- : master complete
I, [2021-08-17T02:56:37.593762 #16190]  INFO -- : Refreshing Gem list

試したこと

JSONの前のバージョンが既に存在しているエラーということで、以下URLを参考に
Bundle clean --force→bundleコマンドを実行しました。
しかし、同様のエラーが発生してしまいます。
URLに書かれているbundle clean --force && bundle update --forceも実施しましたがunicornが起動しませんでした。

https://stackoverflow.com/questions/41649050/rails-why-do-i-get-warning-already-initialized-constant-jsonversion-when-r