I can't tell you for a fact what is causing your problem with the remote. However, I can provide you with some anecdotal evidence of what I have found in general for remotes.
I don't use the Roku remote. Rather, I use a universal remote that controls several devices including my Roku devices. I recently had a problem with similar symptoms. My remote would not respond to button presses, or, it would respond late. I did some research and found out how remotes are constructed. They typically have a rubber membrane that sits below the actual buttons inside the remote. It has touchpoints that interact with the circuit board in the remote. If the rubber membrane becomes dirty (and it will) the connection to the board will not occur. Additionally, the way that you press the buttons may affect how the membrane wears down causing a loss of contact.
In my case, I disassembled the remote and cleaned it with alcohol swabs. I would not recommend taking the remote apart. However, I did not want to purchase another remote. While it improved the performance, it did not fix it.
FREE Windows desktop software for converting Direct Publisher channels to SceneGraph (SDK), for creating
BIF (Trick Play) files,
Roku (MRSS, JSON) feed files, and
FireTV feed files @
GitHub/rrirower.