Cannot connect Time Machine to my NAS

[SteveM55]

Have been using Time Machine to back up my MAC to my NAS without issue until recently.  Now the NAS shows up in the Time Machine but when I try and connect get an alert that tells me there is a problem connecting to the NAS:

"The server may not exist or it is unavailable at this time. Check the server name or IP address, check your network connection and then try again."

I can see the NAS in Finder and log in through Safari (just completed a NAS firmware update).  Any help greatly appreciated.

[chankla]

I'm seeing this too.  On both my RN312 and trusty old ReadNAS 600.

MacOS is 10.14.2 (beta)

Both NAS units are at latest stable firmware available for them

RN312 is 6.9.4 with hotfix 1, Time Machine selected to be in SMB mode.

It starts the back-up and after awhile the 312 NAS drops off the LAN and requires a manual reboot.

On the mode 600, the NAS goes into Checking the file system mode and eventually crawls back to functionality.

Sometimes the backup just stops with the similar error message as the earlier post.

What gives?  Are we the only two people having this issue?