When using the /locate command, it will generate a completely random set of coordinates. I tried to find a jungle pyramid, it dropped me in a birch forest. I tried to find buried treasure, it sent be to an oak forest, which was completely landlocked.
On the original world i found this bug, the fact that /locate doesn't work is consistent. However when I opened a new world to try to "replicate" this bug, it does work. I'm really not sure why, because all settings (normal mode, commands on, structures on, etc) were exactly the same.
Can you provide a seed and coordinates to the world where /locate was broken?