Unusual entry in known_devices.yaml

I am getting a lot of weird entries in my known_devices.yaml like below

samp_3:
  hide_if_away: false
  mac: ''
  name: "\uFFFD\uFFFDs\uFFFD\uFFFD\uFFFD\uFFFD\x1F&amp"
  picture:
  track: false
  vendor:

30 or 40 entries for the last month. Anyone know what is causing it?
I have netgear, owntracks,gpslogger and bluetooth_tracker platforms enabled.

Delete the entry, and then make sure your device tracker is not configured to discover any new devices…

Thank you for your replay, that is what I have done, so far no extra entries.