I've had my Roku Express for probably 2 years or so and just over the past 3 weeks my remote stopped working with only the discovery plus streaming service. It's not the batteries. I'll go to the Discovery plus channel and my remote just won't work sometimes the selections are delayed and sometimes it throws me out of the program completely. This just started approximately 3 weeks ago and I'm really tired of it. Is it Roku's fault or is it Discovery plus fault. I have no problem with any other of the streaming services I have which is Hulu, roku, and Amazon video. Please don't tell me to clear the cache it doesn't help.
When problems are confined to a particular channel, it may be that the channel didn't install properly, that it didn't update correctly, or that the installation has otherwise gotten corrupted. A reinstall may fix the problem, so give it a try.
Remove/reinstall procedure:
If the problem persists at this point, it typically means the current version of the channel app has a problem that must be addressed by the channel itself as they are the ones that create the Roku-compatible version of their app and provide it to Roku.
Discovery plus will not let you delete or remove the software they've taken away the remove channel option
When I try to do a search on Discovery plus every entry I make to each letter it delays and sometimes doesn't do anything backs up I have to wait for it to catch up. I don't have that problem with any other service and I have Hulu and I use Roku and I use all the other TV stations with apps on my Roku and it never happens with any of them only Discovery Plus and then it throws me out of the program back to the Roku home screen
Unfortunately if you're subscribed through Roku you can't do what @makaiguy suggested. You have to cancel your subscription at https://my.roku.com/account/subscriptions and then the "Remove channel" option will appear. You'll still have access to your subscription until the end of the period for which you've already paid. Make sure you try that "Check for updates" option on the screenshot you posted before you do anything else.
For what it's worth, subscribing directly with the provider eliminates that "can't remove the channel" problem. It's usually the same price, sometimes offers more content, and can be used on all devices, not just Roku.
After reading your post again, does it only happen when you search? Once you start a program is everything ok? There's a lot happening behind the scenes whenever you do a search.