After talking to an invisible player and staying in the server for a while, here’s what I noticed:
This only happens when you join mid-game. When you join, you might see a few invisible players. I asked multiple players, including the invisible one, and the player was visible on their screen and for others who had been in the server from the start. This issue mainly affects joining players, and they often end up dying or leaving the game, thinking there are hackers. I hope this gets looked into and fixed ASAP.