PHP-FPM 8.0.16 – Troubleshooting NFS Write Issues

I have a php-fpm (8.0.16) instance that cannot write files to an NFS share. I am using a simple php script for testing:

<?php

ini_set('display_errors', 1);
ini_set('error_reporting', E_ALL);

$fp = fopen('test.txt', 'a');

fwrite($fp, 'test'); 

When running via php-fpm, in a directory that is an NFS share, the following error is received:

Warning: fopen(test.txt): Failed to open stream: Read-only file system in /path/to/nfs/share/test-write.php

However, the following code:

<?php

ini_set('display_errors', 1);
ini_set('error_reporting', E_ALL);

$fp = fopen('/tmp/test.txt', 'a');

fwrite($fp, 'test');

works as expected.

The script works when run from the command line as the same user that is used to run php-fpm both in an directory on an NFS share, and in /tmp.
Additionally, the script works as expected on earlier versions of php via php-fpm.