I’ve recently assisted a developer with the same issue as yours, except his one is a backdoor, yours from the sound of it is a malicious script that teleports people out of your game. If this occurs no matter what, even if you are in a one player server, that means it’s malicious script.
Try do this, CTRL + SHIFT + F, look up for the following words,
- require
- teleportservice
- getfenv
- insertservice
- teleport
- insert
Most likely you have a malicious script hiding in your game, I can help guide you in finding the source of the code and removing it. Feel free to hit me up on discord @ Zenuvius#2480 