I have 13 build 20201112 as an NFSv3 server. The hardware is a Pi 4. The export is mounted on a Mac running 10.14.6. I'm rsyncing to it, and after a while, it hangs.
This is easily reproducible.
The NFS server doesn't appear to be hung as I can manually create files on the mount on the Mac.
Rsyncing to rsync via SSH works and does not hang.