When using a command or command block, you take a seemingly random amount of fall damage upon teleportation. It seems this damage increases with distance, as on the realm I play on, we have a command block zone that you summon a chicken then walk into said chicken to teleport to it as it is over 200,000 blocks away from spawn. If you aren't holding a totem of undying before walking into the chicken, you die instantly upon teleporting, and all your items get left where you were before teleporting. The death message that plays suggests you died of fall damage: "[Username] fell from a high place". This bug is very inconvenient as we also have a teleporter to an experience farm for repairing tools and armour etc, but players die before they are able to reach the farm because they die on teleport. Sometimes it will be 4 hearts of damage (w/ feather falling IV), sometimes it will be 2, or sometimes it will be instant death. Its always a gamble if you don't have any totems. Thank you for reading my bug report, if someone is doing so.