SyncMe Failed to connect to computer, isConnected failed: ECONNREFUSED (Connection refused)
Looks like the settings were fine.

I even had that Samba thing set up right.
I turned that Samba on-off from the router, then I removed the "Computer" from SyncMe, re-added, and it worked.

The error actually happened again, later on, with the "could not delete + sharing violation". Then I did the above steps again, and it worked.

I didn't have long filenames or anything weird like that, but I had a lot of files to back up (first time sync)
I am curious if this error will persist later on, when I will have a lot less files to sync.

It currently works fine.