I don’t disagree in principle, but I have QNAP251+ (relatively new) with a ram upgrade wired directly to the Zidoo (this removing any network issues in theory), and have quizzed many different forums on this subject, and most come back to say it’s not/ shouldn’t be the NAS. I also noticed a material improvement in performance loving from the Vero to the Zidoo, so put it down to the player.
On saying that, I also have a shield tv which I tried using Kodi (Also directly aired to the NAS) and it also failed on the same files, suggesting it was the files themselves. However, no one else has reported any issues with those files, so back to square 1 somewhat...