This time another message is seen in the wsyncmgr.log also, "DB Server not detected for SUP <ConfigMgr FQDN>".
In the WCM.log there's another error message seen: "Source file C:\Windows\TEMP\********.cs" could not be found. That's a nice one!
For me this did the trick:
- Assign NETWORK SERVICE permissions on the Windows\Temp folder (List Folder/Read Data & Delete)
After that WSUS synchronisation is running fine again! This permissions are needed to let NETWORK SERVICE write to the folder.