All inventory and exp lost when joining players try to rejoin world

We have three people playing in a world on Xbox one.  Two days in a row now, after saving and exiting a world -when player two,or player three joins the world - they loose all progress.  They respawn with nothing, and all their previous items like dogs do not recognize them as their owners.  This is very frustrating for a 7 and 9 year old to loose everything twice in two days.