Hi, I bought a new 80 gb hard drive for my iPod 5.5 recently, after connecting to iTunes I got error -1416. I have tried different computers ( Mac Mini 2010 / iMac 2010 / iMac 2014 / Acer Win10 ) with the same result, I cannot restore/format the drive without getting POSIX...-devicebusy error. I have tried all solutions (as suggested above) with no luck, only Terminal $sudo diskutil zeroDisk /dev/myiPod worked, but still cannot restore it!
I can boot into diagnostic mode, HD-SMART test displays regular new-and-working hard drive info, so I'm thinking about replacing the flex, connector cable and battery (it charges only to 10%) to see if one of these three or maybe all are making the difference.