Hupn Hann

It doesn't happen every time, try 2-3 times then the bug should occur for sure. I used a netherportal for quick chunk unloading, but I guess the tp command should do as well.

Pistons still disappear in 11b. It varies, sometimes the pistons break, sometimes the sand drops. Either way it should be fixed

A pretty annoying bug indeed, especially when fighting a big group of mobs. Still present in 11b.

Still present in 14w10c

The baby cows were fixed in w10, however the chicken were not...

I get the point with glass and other blocks a blaze could possibly see you trough, but not halfslabs. And I mean trough a solid floor/ceiling of halfslabs, not a wall with gaps. It's just annyoing as hell.

Still present in 14w06b. Would be nice if someone could update that.

I can confirm that, blaze also track/attack trough halfslabs, very annoying.

I can confirm that problem. It occurs when the chunk with the piston+sand is unloaded while the contraption is active. You can reproduce it by hooking a bunch of pistons with sand ontop up to a clock and entering and leaving the nether a few times.

Edit: I attached 3 screens of a test setup which can be used to reproduce the issue.
After coming back from the nether (portal directly next to the setup) one piston was missing (and 3 sand broke into items, but that isn't the main issue here).

Edit 2: The issue can also be reproduced by unloading the chunks normally by walking away, so it is not related to portals.