If anyone has this issue and you are trying to use multiple join / left rooms like I was doing, make sure to always be joined in one room.
In my case I was leaving one room before join the next one, so I moved the oldroom.leave() action inside the newroom.onJoin() and now everything works fine.
Note, this was happening randomly at the beginning until I overloaded the room onInit with data, then I got the issue all the time because the second room was delayed on load.
Best,