Random players appearing in my lobby

Product: Apex Legends
Platform:PC
Please specify your platform model. PC
AMD or Nvidia Model Number 4090
Enter RAM memory size in GB 64
What is your gamertag/PSN ID/EA Account name? PLSTOLSKLN
Please provide your squad mates' gamertag/PSN ID/EA Account name if possible.
Are you using any software with an overlay? No
Which Legend were you playing (if applicable)?
Which Legends were your squad mates using (if applicable)?
Where did the issue occur? In the lobby (waiting area before the match)
Which part of the map or menu were you in? If you don't remember the exact name, please describe the area or what you were trying to do in the menu. Lobby
What were you doing when the issue occurred? E.g. respawning a squad mate at a beacon, using an ability, a squad mate left the game. Just finished a match
Did your squad mates also experience the issue? Yes
How many matches had you played in a row before the issue occurred? 1
When did this happen? (dd.mm.yy hh:mm) 15.09.23 15.00
How often does the bug occur? Rarely (0% - 9%)
How severe is your issue? Minor impact to gameplay
What happens when the bug occurs? I had a random player appear in my lobby. They were possibly in my last match but I have my lobby set to private so how/why did they appear?
What should be happening instead? Other players should not be able to join a random private lobby
Steps: How can we find the bug ourselves? Set full privacy for lobby and see if someone can join you who is not a friend etc.

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Here's my lobby settings:

Here' the random player appearing in my lobby: