Filesystem Remounted when cd into it

Question

I have run into a strange mount/umount situation

On the initial setup I had

1. NFS Server

   IP: 10.22.10.10
   Shared Filesystem
    /mnt/exported

2. Application Servers

   Directory to mount shared filesystem

    /mnt/shared

Mounted filesystem

    mount -t nfs <ip-nfs>:/mnt/exported /mnt/shared

3. NFS Server

   Renamed Shared Filesystem

    /mnt/exp

4. Application Server

   Renamed directory to mount shared filesystem

    /mnt/sharing

Unmounted initial shared filesystem

    umount /mnt/shared -l

Mounted new shared filesystem

    mount -t nfs <ip-nfs>:/mnt/exp /mnt/sharing

5. NFS Server

   Removed the initial shared filesystem

    rm -rf /mnt/exported

6. Application Server

   Tried to remove initial directory for shared filesystem

    rm -rf /mnt/shared 

However, I'm not able to remove that initial directory, the remove command just hangs I then also noticed that when I ran the command df -h it would just hang, had to kill the ssh session. I also noticed, that whenever I ran a command that would access /mnt/shared it would remount the filesystem, even if it the shared filesystem on the NFS server doesn't exit anymore.

Any thoughts what might cause this. Is the best solution to reboot the application server?

Thanks for any info.

Cheers, Roland