When ever you enchant a trident with riptide enchantment. Then you fly with your riptide trident so, there is some small chance that riptide trident sound not play then you will fly in sky after some seconds you will died in middle of sky without any reason. In death message it say "(Player) fell from high place." And you were in middle of sky and don't touch the group yet. So, it is bug of minecraft and it is very bad because you died instantly without any reason so, fix this bug as soon as possible. Also I cannot give any photos but you may try why self and fly 20 times in sky to happen because it sometime happen and sometime not.