The CSS I updated in the local virtual environment built with VirtualBox was not applied even if I deleted the browser cache, and I was in a situation where I couldn't check it, so I'll leave it as a memorandum.
Apache configuration seems to be a factor, and I solved it by setting the following in httpd.conf:
EnableMMAP Off EnableSendfile Off
For Apache documentation, please refer to the following link. https://httpd.apache.org/docs/2.2/mod/core.html#enablemmap https://httpd.apache.org/docs/2.2/mod/core.html#enablesendfile