Using the setup below the diamond block connected to the slime block seems to be occasionally duplicated. The blocks may actually be Block 36, and remains in world upon quitting and reloading in Single Player.
Setup used:
http://s2.postimg.org/5pyr2obq1/2015_03_05_21_12_25.png
clock ----> pulse shortener ----> delay manager ----> piston & slime block
Related issues
Comments


Sorry.
Also, ghost blocks remain in world when world is saved and quit, then reopened.

Are you sure? That would mean this is a different bug.

Ah. No, I placed the block in the ghost block's space without realising.
Dupe of MC-54026.