Many file permissions have automatically changed

All of a sudden I see many file permissions have changed from 644 to 640

Due to this I guess , getting errors like

2020/10/14 10:57:27 [crit] 25979#0: *846 open() "/var/lib/nginx/tmp/client_body/0000000007" failed (13: Permission denied), client: xxx.xxx.xxx.xxx, server: xxxxxxxxx.com, request: "POST /xxxx.php HTTP/2.0", host: "xxxxxxxxxx.com", referrer: "https://xxxxxxx.com/xxxxxxx.php?action=xxx"

Please suggest.

Fix permissions option is not fixing this.

Is the topic here https://forum.centos-webpanel.com/index.php?topic=9526.0 related?