Check your /etc/ssh/ssh_known_hosts on the local machine. It seems that you have an outdate fingerprint for pve2 (10.0.1.5).
How are you connecting to the server? Is this from a local ssh client or are you connecting via WebUI?
A `pvecm updatecerts` might help.
I ran that command on all my nodes - it seems to be working ok now. I think pve2 showed that error possibly due to my browser being wonky. It was showing it when I went directly to the Shell via Proxmox web GUI. I hadn't tried SSH. I didn't get this when I rebooted and re-logged into Proxmox with a fresh browser.