My remote works then stops working. I take out the batteries...it worked and the next time I go to use doesn't work. I've re-paired it with the box...works...then not working. All of this started when I used the headphones to listen which made the box itself reset. I want to be sure that I need a new remote and the correct one.
Happens on all my Rokus occasionally. Sometimes I rotate the batteries, other times just a light tap in my hand. Just a roku quirk I think, doubt you need a new remote (will probably do the same thing). Probably just temporarily loses connection and the battery trick reestablishes the connection. Happens on the RokuTV as well as my Premieres and Ultra players so not unique to your Ultra.
I have discovered that if I tap the remote too hard, it will reset my device.
I have found the universal streaming remotes compatible with Roku the way to go if you want to eliminate the hassle and just use the roku remote or the Roku App for private listening or voice searching.
@Tivoburkee is the remote man here though. Maybe he has some suggestions and better answer for you.