MQTT Presence Detection weirdness

My Home Assistant keeps doing this

That is, it’s registering my iPhone with OwnTracks installed multiple times as s, st, ste, steve and then lots of steve. I delete these entries from known_devices.yaml, restart and they all come back.

Does anyone know what could be causing this? My configuration is on Github if anyone wants to have a look but it’s very straightforward.

Example from known_devices.yaml

stev_iphone:
hide_if_away: false
icon:
mac:
name: stev
picture:
track: true
vendor:

ste_iphone:
hide_if_away: false
icon:
mac:
name: ste
picture:
track: true
vendor:

s_iphone:
hide_if_away: false
icon:
mac:
name: s
picture:
track: true
vendor:

Thanks

Steve