I have been having an issue where multiple blocks (no where near each other) are being destroyed at the same time.
I have noticed they seem to be the blocks that are dimmed (despite setting their z axis to -3) Update: Scratch that, it was coincidence. After more testing it showed there was no correlation between dimmed blocks and multiple disappearing blocks.
The code seems to work for almost all other blocks, see [pastebin]http://pastebin.com/in8Svs93
I am wondering if the objects are linked (i.e. treated as one object) and if that might also be the reason they are randomly appearing at the back of the scene.