Wirelless connections are problematic for streaming. They basically have to be “perfect” so that max signal transfers occur between router and receiving units. Wired is always better. You have also changed from a G band to an N band router. Although N band is faster than G, it does not have the range of G. I had a similar problem when I upgraded from G to N. Since the WD will receive the N signal and not the G anymore, it is dealing with a weaker signal now, and it took some fiddling to get a good N signal into a room that was fine with G. It took better positioning of the router and its antenna and changing broadcast channel of router.
To help you do this, too, download the free program inSSIDer from metageek.com (there are versions for various platforms, Win, Mac, etc.) Read the user guide there and install inSSIDer. With this program you can see your wireless signal and all others around you. If you have a dual-band router you can fine tune the 2.4G and 5G signals for max effect. Use a laptop you can move around with to view the signals, their strengths, etc. Select the best (least crowded and strongest signal from your router) 2.4G channel from 1, 6, or 11. Do same for 5G channels. Fortunately, you have adjustable antenna on the router, so adjust your router antenna for best results and turn your router if necessary. By using inSSIDer properly and effectively, you can squeeze blood out of a turnip.