I was mining away in the nether, and I decided to go back to earth. So I hoped back into the portal and when I appeared on earth I had discovered that the game generated a new portal in a large unexplored cavern underground a ways off from my castle and made me come out of that portal instead of the one in my castle. Every time I leave the nether I now appear in this cavern, out of a portal that I did not make. Does anybody know what happened? Has this happened to anyone before? Why is the game doing this?
It is a random occurence, if I remember. It does happen and it's on purpose (for the most part). Break that portal down and I think it should link to your main portal again. If that does not work, you can read this part of the wiki here and figure out how to make it link to your main. You will probably have to break the portal in the Nether, or build a new one closer to your home portal if I am right.
break both your original portal and the new one it generated. Build a new portal 1 block away from your old one. That fixed it when it happened to me in one world.
Yeap, try it, that`s true.
Also the reason may be in exact block you stay when teleporting. The left one may be closer to your original portal - otherwise the right one to another (by the rule of closest 128 blocks per 8x dimension, read wiki).
We're setting up the Nether network on our server (as it magically got deleted during the 1.0 update for some reason). Here's what happens.
RW Portal > Nether Portal goes to the correct destination.
Nether Portal > RW Portal generates a new one a couple hundred blocks away.
This happens for one person.
My guess is that the portals are *just* barely far enough from each other that the portal lock is messing up. Move the portal in the Nether closer to the real world's coordinates.
Stand in front of your portal, get the X and Z coordinates in the real world, and then plug them into this calculator. Place a new portal in the Nether at the appropriate coordinates. Your problems should go away.