This is not expected behavior. An older version had pessimized locking which preventing concurrently adding a file to a directory and listing the directory simultaneously which is the most similar symptom. I recommend upgrading to the latest version, running with debug flags `-f -d -o curldbg`, and observing what's happening. Please open an issue at https://github.com/s3fs-fuse/s3fs-fuse/issues if your symptoms persist.