MCPE LAN play - 3 player limit

MCPE LAN Play

Hi,

So my nephew and niece are visiting and together with my kids they all want to play Minecraft. Four kids in total so should be fine with the 5 people limit. Trouble is three of them can join no problem and then the fourth, no matter what device they are using, generally can't join - either because:

1) The world just won't show up in the friends tab or

2) The world shows up (eventually) but when joining it says "Unable to connect to world" or

3) Sometimes the fourth player can get into the world but they crash out within a few seconds.

So seemingly despite there should be a 5 person limit I actually only have a three person limit!

It doesn't appear to be anything obvious - i.e. all devices are connected to the same wifi, and they are all running the latest edition of MCPE. I'm thinking it is a router/bandwidth problem but I am kind of clutching at straws.

Basically anyone got any clues?