Hey @dfriou
Thanks for posting here in the Community!
Have you tried all the troubleshooting steps in this Support article: How to resolve issues with your Roku® simple remote or Roku voice remote?
Since you also have a Roku Streaming Stick+ 3810 that can be connected directly to an HDMI port on your TV, wireless interference from the HDMI connector may impact the performance of your remote. Try moving it away from the HDMI connector on your TV by installing a free extension cable.
Please keep us updated.
All the best,
Kariza
Kariza D.
Roku Forum Moderator