Kumasasa, I don't think that was the point of the issue, he was trying to replace a block either an air block, yet it ended up as this. What I wante d to know is which command he used to do this, so I could see if it is a bug for everyone or not, because it may be very specific so the usual "/setblock x y z minecraft:air replace" or a "/fill x y z x y z minecraft:air" may work while something more specific wouldn't such as having an operator such as masked or replace.
With what command did you replace the block with air? I want to test it out myself.
Looking at how things were affected in this update I would say that we have been seeing two different bugs/game mechanics actually occurring.
The first bug/mechanic is when when hoppers are stacked vertically. Hoppers constantly try to pull things out of the hopper above them. Prior to 13w10a, when hoppers did their pulling was rather unpredictable. To demonstrate this unpredictably build a tower of 4 hoppers when a chest at the top and bottom and comparators + repeaters reading the levels of every hopper. If you put a stack of items in the top chest in 13w09a/b/c some of the repeaters with light, some will blink and some will just stay off. It appears as if there is no ryhme or reason behind the pattern as it will change if you rebuild the test in a different location or re-log. In 13w10a, the test stack becomes more predictable, but it still does not match up with what is expected as only the bottom repeater will light up for me, no matter the stack size or if I point the hoppers down or to the side. Watching the slots in the hopper tower it seems that hoppers are sucking items before the comparitors have had a chance to update, and since the bottom hopper doesn't have anything sucking items from it, one item appears to get stuck until the bottom is not able to suck stuff from above.
The second bug/mechanic was visible prior to 13w10a, and it occured when items were moving sideways through hoppers. Items would seemingly skip hoppers and not get sucked down by hoppers below. This seems to be related to MC-10679, as it now works correctly in 13w010a.
I'm sorry, I have been inactive for quite a while. the seed is 248903167067004858