Two days ago I attempted to go back to The End, which I had not visited in a month. I had a trail marked to get to the stronghold, though when I reached the Village that the stronghold was under, the cave I had dug was gone. I acquired more Eyes of Ender, and upon throwing them, they lead me to an entirely different area. I ran out of eyes, but it appears that the stronghold is no where even close to the old one.

This is the same world I have been playing in for over a year, and I've also noticed that I'm getting serious lag in areas around the old stronghold as well as at my bed/original spawn location.