Put the summary of the bug you're having here
The bug of the nether portal can lead you to the position.(I am a Chinese,so I am not good at English please forgive me.Thanks) For example the nether portal in the main world:X:500 Y:30 Z:1000 then you go into it and ++before you are transported ++if at that time you close or disconnect from the server and then you go back to your sigle save or server again you will find you are find you are going to be at :X:500 Y:30 Z:1000 in nether(absolutely you will swim in the lava or dashed(jump from a high place and die) because you do not know whereis you will be transported in nether.And you can also do it in nether but this time you will be transported to the main world In the corresponding coordinate position (I use the translate machine to translate my meaning) if you can not understand I will give you another example the portal in nether X:2500 Y:15 Z:8500 and repeat the way I describe you will be transported to the same position(X:2500 Y:15 Z:8500 )in the main world(If you do not die ,you can not get back beacause this way you will not get another link portal)

What I expected to happen was...: Obviously I want minecraft be bugless(Chinglish) and more perfect.So I hope you can fix it.
Describe what happened here
Imagine you are in a server,the network quality of the server is not good(or the server is busy people online)and you want to transport from the portal and when you go into it the server is not available to deal with your request then you are unexpectly be transported to another unkonown place or you die faraway what is your felling.Well that is my story and this bug is used bu some people and I unluckily try it.

Steps to Reproduce:
1.choose a place no matter in main world or nether
2. go into it when it will transport or loading the area disconnect(server）or exit from(shutdown) the game(single game) try a few times if it not work
3. you will see or discover what I describe.