In what context is the access.log used? Is a WordPress installation running there? If so, can you see any correlations between requests/calls to the WordPress website and this entry in the access.log?
Which PHP version is used?
If you suspect a connection with WordPress, could you deactivate all plugins in WordPress and activate a default theme? Do such entries still appear? If not, you can switch back to your theme and reactivate the plugins piece by piece. Maybe you will find the guilty component in your project.
Alternatively, you could also enable debugging in WordPress as described here: https://ww.wp.xz.cn/documentation/article/debugging-in-wordpress/
