Internetclient does not find local backup server and backup slow and slows performance a lot


I am backing up a few laptops over the internet.
But my Laptop also is in my LAN of my Backupserver (sometimes) and it does not find the backup server locally, even I have disabled the setting that it should only use internet server.
My Laptop is connected via Wifi and the DNS of my backupserver gets resolved in my LAN to the local IPv4 Address of my Backupserver, so actually the transfer happens not over the internet, but locally (also visible through the speed, because it is faster than our ISP provides/we pay for).

Also if I backup this Laptop or another one at home or from another place it takes days to finish an incremental backup. The Laptops are almost not usable in this time, as the backup process takes almost the whole available bandwith away.

I read and thought about buying the block tracking tool, but don’t know if it would change the load in my case.
Also on local network with a client connected via LAN with 100 MBit/s (working towards GBit/s).
It says it needs to take 2 hours for an incremental image backup of an 220 GB SSD.
He refers incremental on the last full image backup which was taken on 22th of May 2020.

Starting scheduled full image backup of volume “C:”…
Transferred 143.024 GB - Average speed: 94.3156 MBit/s
Time taken for backing up client Local-LAN-PC: 3h 37m 30s
Backup succeeded

So an incremental backup takes around half of a full image backup.
Is there any information I can send for debug or screenshots for the settings?

Not finding the local server means the server broadcasts are not reaching the client.

This can be caused by:

  1. firewall settings on the server
  2. firewall settings on the client
  3. an intervening router blocking broadcasts

My guess is that you have checked the first two causes but have a problem with the third.

The WiFi access point can block broadcasts as part of an optimization of radio utilization. See the post Wireless interfaces are not able to see UrBackup server