In Linux running over NFS, .nfs files are created when a file opened on a client is deleted from the file system while still opened. The client renames the file to a fairly long string like you're seeing in order to discourage other clients or processes from using the file.
Usually you can find out what process is causing using the lsof command, in this case:
This will output the process that is working with the file, and if necessary, you can then kill said process.
What are EFS files starting with .nfs?asked 4 months ago
Unable to write to EC2 instance running Apache on shared EFSAccepted Answerasked a month ago
Log file owner is root instead of webapp - Ruby 3 on Elastic Beanstalk on Amazon Linux 2asked 17 days ago
Minimal latency for EFS OPEN(new file), WRITE(1 byte), RENAME and REMOVE?asked 4 years ago
How do I save data files to EFS using a Node.js application?asked 4 years ago
Is it possible to make EFS publicly accessible?asked 10 months ago
EFS - NFS Client Error while creating a directory or file: Remote I/O Errorasked 2 years ago
React webapp - each source file rendering index.html sourceasked 2 years ago
Cannot get a VPC-peered EFS accesspoint to mountasked 4 months ago
WorkMail webapp: Creating rules from messagesAccepted Answerasked 4 years ago