Multiplayer, players dragged into void, textures break down, extreme lag.

(My internets not the best) whenever a player joins my survival world, I get disconnected from, and unable to rejoin my Party and the player who joins begins to freeze up,  lag, textures load incorrectly, get killed by an unsee-able mob and in rare cases sink into the void and teleport across the map.

I've experienced similar problems whenever playing multiplayer and players are not all in close proximity to each other (in this case we were a map apart)