All you need to do is go memory and clear your system cache. then open minecraft and don't update. Enter your world and do the duplicating glitch the same as before the patch.(Set a dispenser down then a tnt behind it. hit the tnt and open dispenser and put whatever you need to duplicate inside it). after your done just save it update and there you go.

I will find a video to help explain this if needed. I hope this helps.
If you need more help feel free to message me or add me on xbox...AMonotonePanda