World stopped allowing achievements to be unlocked even though no setting were changed on the world and as remained in Survival Mode - Normal. 

I have since attempted to recreate the issue to no result.

I created a new world, made a crafting table and what not, and closed the world. I copied the world and turned the copy into creative and see if anything affected the original world, with no result. I then created a beta of both the original world and the copy and nothing has affected the original world. I then put myself into creative on the beta copy and went back to check the original world and nothing had changed. The original issue of the original world happened around the 12th of December and since then I haven’t opened the world or made any changes.