problem with blocks levels

I'll do my best to explain my problem. 

I loaded my map. I saw that there was new "mountains" that didn't existed before. You can see the strange "mountains" in my photos. There's one in the middle of my house (and I lost my chests, all my stuff...)

I think that deepest levels blocks has gone up. Some blocks from deepers layers are now higher. They are forming strange "mountains".

Is this enough informations ? 

Thank you