All of things in spawn chunk are reset. It's hard to describe. I was making map making technics by command blocks, and all in the spawn chunk blown when I start this map again.
Summary : JUST RESTARTED THE MAP, AND ALL IN THE SPAWN CHUNK BLOWN.
Screenshot 1 : While activating this map. I was making custom /clone command. No size limit, include rotate/mirror functions, but slow. It clones progressively, and randomly. It was activating over than 100 commands per tick. (include execute individually)
Screenshot 2 : Before restart the map.
Screenshot 3 : AFTER (All hopper clocks disappeared)
p.s. Also there are similar bug that some world(not ALL worlds) before 15w36a is not compatible with after 35e.
p.p.s. I don't know about deep programming knowledge. I did my best to describe.
Is this still an issue in the current Minecraft Snapshot 15w44b or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.