Minecraft wiki entry for Development_versions, associated text: MC-133713 – /spreadplayers and /worldborder suggests X/Y instead of X/Z when nothing is typed.
MC-135392 – Dimension arguments fail to properly serialize, breaking "/chunk in" and "/execute in" in multiplayer.
MC-135398 – /chunk (force|unforce) with /execute store success.
MC-135424 – Relative coordinates cannot be used with /chunk.
MC-135426 – Cannot tab-complete chunk coordinates in /chunk.
MC-135428 – /chunk targets the overworld by default and not the sender's dimension.