I have recently put 4 Roku Ultras into use at my home. (Replaced 3 xFinity X1 boxes with the xFinity Stream (beta) app) and out of the 4 devices, I have one that frequently becomes "jittery". The Roku menus, all inputs from the remote, and the cursor around app tiles become very jittery. slowly navigating the menus to reboot the device fixes it, but this has happened every day for several days. No other remotes are in use around it, but there is a Bose surround sound system that takes the HDMI and passes it to the screen.
Is the device hardware defective? I have 3 others that work great. I didn't have a problem at all until several days after the surround sound system was in place. (The whole setup of this hardware is quite new; the TV, the surround sound, the Roku, all of it.)