Issue:
When you put a map at a glowing item frame the player position (not positions) gets rendered as 2 positions.
Recreation:
Create a map, put it on a glowing item frame, and it appears to be that there are 2 people (even in singleplayer!)
Link to drive link for proof:
https://drive.google.com/file/d/1Zxaad-mRHq4wnDHzoNw5UI6KH8oZIO8x/view?usp=sharing
Those markers are not showing the player's position, but rather where the maps are. Since you are in such a large map room, it is expected that there will be many markers to represent all of the maps.