So there is a PART of the chunk that does not appear unless I update where blocks should be.
It is only a part of the chunk, since nothign happens to blocks far above or underneath.
In picture one you see the missing roof.
In picture two you can see taht I update it.. This time with diorite and the area fills with diorite as it was built.
In picture three you can see that I updated it with a redstone block, by placing one above where there should be a block. Then that glitch-area filled with redstoneblocks, even there should be diorite.

First I always updated it with diorite, just because that block is nearby. Recently I updated it with a Redstone block and you see what happens then...