In the debug world, blocks are supposed to appear once.

Some blocks are actually appearing twice. The blocks at x, 70, 185 are also appearing at x+2, 70, 1.

Some blocks known to be affected (probably all of the ones at z=185):
minecraft:stripped_spruce_log[axis:z]
minecraft:note_block[instrument:harp,note:13,powered:true]
minecraft:note_block[instrument:snare,note:9,powered:true]
minecraft:note_block[instrument:bass,note:5,powered:true]
minecraft:note_block[instrument:bell,note:1,powered:true]
minecraft:note_block[instrument:guitar,note:22,powered:true]
minecraft:note_block[instrument:xylophone,note:18,powered:true]
minecraft:yellow_bed[facing:west,occupied:false,part:head]
minecraft:purple_bed[facing:south,occupied:false,part:head]
minecraft:powered_rail[powered:false,shape:north_south]
minecraft:moving_piston[facing:east,type:sticky]
minecraft:fire[age:1,east:false,north:false,south:true,up:false,west:false]