Connection issues connecting to two servers

I’m uploading data from WD to two servers. Server one is my main site and Server two a back up.
The problem i have is when i have an issue with Server Two being down data is also not uploaded to Server one.
Kind of defeats the purpose of having a back up really. I’m using the traditional method to FTP to Server one and the Update to a second Server function in WD for Server Two.
Basically when Server Two goes down i need Server One to keep working normally with no FTP stoppages.
Any ideas?

its not clear to me where and how you have this setup in WD exactly?

I’m using the default method to upload data to first server. For server two i go Control Panel/FTP Connections/General FTP( to ftp non WD files or WD files to a 2nd server) Ist Setup. I enter the details of my second server here and what files i need to upload.

I will look into this next week, I am away this weekend

Thanks Brian, Much appreciated