I’ve seen a few old post with this issue but nothing new. I am away from my server and trying to sync a fee items and they are getting stuck at 50% and not downloading any more. Is there a known fix for this? Many thanks 
I had same problem with my sync, all stopped at 50%, ie transcoded but download would not start, in my case it was a sync entry that was stuck on another device, when I deleted that sync entry all other devices started to download.
