Known_devices Nmap & Fritzbox

I’ve got some kind of issue with the known_devices file, created from nmap or Fritzbox… Even if i copy another yaml document and name it known_devices.yaml, this issue shows up…

First time after enabling nmap or fritzbox everything just looks fine - all components which should be shown as home, are showing up, but when I want edit for example add a picture for a device and then restart home assistant, the known_devices file adds all the already known devices again and this behaviour repeats everytime HA is restarted.

So after a few times of restarting the known_devices file has over 1000 lines, but in the HA interface all devices show up just once.

What I’ve noticed regarding this issue is (but I don’t really know if it matters), that the coding in the known_devices file changes from UTF-8 to ANSI everytime HA is restarted

Does anyone have a similar issue? Or knows how to get this working?

Thanks in advance