Statistics does not have all blocks and sometimes resets.

In the statistics menu you are able to see all blocks and how many of them you have mined in that specific world. I expected it to not reset and to have all blocks.

But it didn't have all blocks and sometimes it resets.

I don't know what I did when it resets but to see that it is not all the blocks follow following guide.
Steps to Reproduce:
1.Press esc.
2. Press the statistics button.
3.Click on the blocks.
4.See, not all the blocks are there.