Redmine

Thanks for quick advice!
I confirmed that running "bin/rails tmp:clear" solved the issue.

From further checking, I found that the issue cause was the followings.

1. I created "ja.yml" file on 1 plugin with invalid "en:" key on Redmine 4.0.3 environment.
   (I forgot to replace the key to "ja:" after copying the file from "en.yml".)
   

   redmine
     +- plugins
       +- redmine_xxx
         +- config
           +- locales
             +- en.yml
             +- ja.yml (invalid "en:" key)
       +- :
   

2. Before checking Redmine itself, I removed all plugins, but I didn't execute "bin/rails tmp:clear".

I am so sorry for bothering you by my mistake.