Master Client Disconnects When Second Player Joins

Hi. Sometimes when I have a single player in a room and a second player joins, the first player will disconnect. I tried finding the reason for the disconnect and the message is "DisconnectCause.DisconnectByServerReasonUnknown". The PUN logs don't seem to say why it's happening either. Usually this happens when I leave the first player in a room doing nothing for about 2-5 minutes and then have another player join which disconnects the first player. Is there some sort of AFK timer that triggers this even though the game is running (not in background)?