Ipod classic 160GB flash at end of sync

I have been having issues to sync my iPod since I upgraded to a new iMac, whenever I try to download or update music on it though Music/iTunes, it's becoming a bit of a pilava.

It was all ok till a couple of days ago, still struggling I decided to reset the iPod and start from scratch, I wish I did not do that... I updated software, reset it, iMac sees the iPod, sync is working too, but at the end of the procedure, when I eject it and it disconnects itself, the iPod flashes as it turns itself off and on asking to set up the language, as when you set it off on for the first time, no data/music downloaded to it. Try several times, changing slightly w/o iTunes but through Finder, same as above, at the end it flashes and turn off/on.

Any suggestions please? Really appreciated