Cannot find some source code (404 error) after upgrade gitlab


We are using self-hosted gitlab on AWS EC2.
Recently, we upgraded our gitlab version from ver.11 to ver.14.

Upgrade itself succeeded without any interruption or error.
However, we sometimes faced the issue of ‘source code not found (not all of them)’ after upgrade.
Before upgrade, nobody faced the issue.

The strange thing about this issue is that the source code which is not found in gitlab is still alive, because we can see the source code if we cloned the repository to local machine.

This is our nginx log when a source code could not be found.

2022/03/18 18:26:50 [error] 10125#0: *23 FastCGI sent in stderr: “Primary script unknown” while reading response header from upstream, client: **.**.**.**, server: _, request: “GET /gitlab/our_project/our_repository/-/blob/develop/public/index.php HTTP/1.1", upstream: “fastcgi://unix:/run/php-fpm/www.sock:”, host: “”, referrer: “”

Is there anyone who had same experience and solved this issue?

if you need more info to specify the cause of the issue, please let me know.
Thank you.