The problem and causes
For what it's worth, this applies to nearly any remote control… Some of the buttons on my Google TV (link to a review of it) remote were going bad. When pressing a button you'd get no response, you'd have to press very hard, you'd have to press several times, or sometimes one press would be treated as several presses. And most of the information I found on the internet about how to deal with this problem was wrong.
This isn't due to the bluetooth remote needing re-pairing with the TV dongle as many people believe without any good cause (if the control needed re-pairing with the dongle, none of the buttons would be working). The same kind of people think that continually re-installing software fixes faults with it, expecting that doing the same thing repeatedly will produce different results. Bad code is bad code.
Nor was it due to the batteries going flat, even though that one is a reasonable assumption. Yes, some functions of a remote can fail while others still work with bad batteries. Once the batteries are too flat, if some functions take (fractionally) longer to complete, or use one more transistor than other buttons, a too-low battery voltage can go that little bit too much lower and fail. Then when you stop pressing the button it recovers a little bit, and some other things still work. Also, if some buttons don't conduct fully, they may fail with a flat battery, but still work with a good one.
In my case it was due to some of the switches going bad, a fault that's existed with TV remote controls ever since they were invented. There's a number of ways that remote control buttons can fail:
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If the remote has actual switches, the switches can fail, or the soldering between them and the printed circuit board. You have to resolder them, replace them, or somehow prise the switch open and try to repair it.
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If the buttons work by pressing a conductive carbon and rubber pad against some circuit board tracks, the rubber often crumbles (sometimes microscopically) and leaves the tracks permanently coated with bits of conductive material. Cleaning the tracks and pads usually fixes them, all you need is something like metholated spirits and a cotton bud. Sometimes you have to put a conductive metal sticker over the pad, so the metal sticker bridges the circuit tracks instead of the hard rubber pad.
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Sometimes the buttons are part of a flexible rubber-like strip that goes all gooey and sticky. It's the plasticiser leaching out, and it will continue to do that forever. It can make the buttons sticky to press, not release properly, feel icky to use, and sometimes the fluid can get into the electronics and make it misbehave. All you can do is clean it out, again and again. Peel off the rubber panel, wash it thoroughly. Try dilute dishwashing liquid on the rubber/plastic parts, it's a safe cleaning solution for you to use. Dry it off. Clean it with alcohol. Clean any dirty circuit board tracks with alcohol. Wipe it off. Let any still-wet parts evaporate dry.
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And sometimes, as in this case, the buttons press a bit of domed metal causing it to pop into the opposite shape, and touch some of the traces of circuit board.
The domed metal kind of switches can fail in several different ways:
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Metal contamination (either during manufacture, or air polution later on). Cleaning them fixes this. And this is where using some proper contact cleaner will probably be better than just alcohol.
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The metal dome loses its shape, and no longer springs into its two positions (resting and pressed) properly. Your best bet is to swap the metal dome from a failing button with a working one from a button that you don't use. This also happens inside tiny tactile switches (a clicky switch mechanism that works in the same way).
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Some of the circuit trace got scraped off. Sometimes conductive paint can be used to rebuild some part of it.
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The metal dome can slip out of its position. You'll need to reposition it.
In many cases the metal dome is stuck into place with adhesive, perhaps under a strip of tape. Sometimes there's an insulating structure between the circuit board and the metal domes, and you'll need to ensure that they pass through any holes in the right position. The dome will bridge between at least two separate contacts, that could be an inner and outer circle, it could be a set of spiral tracks, zig-zag tracks, or interleaved tracks.
In my case, it seems that the contacts just needed cleaning. The hardest part was getting the remote apart without mangling it, then getting it to snap neatly back together again. The easiest bit was spraying some contact cleaner onto a cotton bud, and giving the contacts a couple of wipes with it.
If you use proper electronics contact cleaner, it should prevent the problem recurring for a long time. Don't use sprays like people use on things like petrol lawnmowers with spark plugs, they're corrosive. I found “Servisol electrical cleaner and lube” contact spray to be quite good, and far cheaper than any of the DeOxit sprays.
Disassembly
Take off the battery cover and remove the batteries.
The casing is held together with plastic hooks and loops in the top and bottom halves (look at the photos below—note there is no catch near the volume buttons, and you can click on the images for a large normal photo). You'll need to press into the plastic to release them, prising the back half outwards away from the top half. I used a spudger (a thin, blunt-edged, wide-bladed, tool), starting at the battery end. Releasing the battery end, working my way alternately up both sides to the other end, poking my fingernails in to keep the halves apart as I moved along.
The circuit board is screwed and clipped into place. Remove the mini torx screws, and gently prise the clips apart to release the board. Again, I started from the battery end.
At this point you may want to blow and wipe out any dust and fluff that has got in.
You can put the batteries back and find any buttons are giving you grief, mark them or draw a diagram of their position. Then take the batteries out again.
Carefully use a thin knife (I used a minature box cutter) to peel off the white sticky tape around the problem switches. It's only adhesive tape, not any part of the circuit. If you damage bits of it won't matter.
I only exposed the problem switches, that way I don't have the grief of trying to reposition everything when it comes to reassembly, nor risk introducing extra faults.
You can see that the metal domes are attached to the white tape, and there's a thin clear insulating tape over the circuit board with holes in it, which the metal domes pass through. When the buttons are pressed, they electrically join the outer copper ring to the inner circle with the crosses on them. Barely visible amounts of tarnish on any part of the contacts can be enough to cause them to misbehave, so a decent scrub with proper electronics contact cleaner is recommended.
Dampen a cotton bud (or something else) with contact cleaner and wipe the contacts and the metal dome. Wait a moment, then put the adhesive tape back into place, making sure that the metal domes are completely inside the cut-outs on the clear insulating tape. The metal domes have to sit on the outer copper ring to be able to connect the ring to the inner section when they're pressed.
I was being cautious, since disassembly and reassembly is a pain and potentially damaging, so I put the batteries back in and tested the remote as a bare circuit board.
Satisfied all was well, I fitted the circuit board back into the top half of the shell (slightly hooking the infra-red LED at the top under a bit of plastic in the top shell first). Fitting the board is fiddly, you have to get it into the right spot for some plastic pegs to fit through holes in circuit board, and the retaining clips to grab around the edges of the board. Then put the screws back in.
Again being cautious, I fitted the batteries and tested all the buttons. Many years of electronics servicing has taught me that things do pop out of place, and the less times you disassemble tricky things the better.
Finally it was just fitting the back of the case into place. I lined it up, then pressed it together flat—all sides at the same time.
Modifications
While it was apart, I decided to permanently solve the problem of accidentally pressing the Netflix button. I don't have Netflix, and I don't ever intend to get it. So I removed the metal dome from above its button. In the photos, you can see a bit of a texta mark on the white sticky tape next to that particular button. A less permanent solution might have been to put something insulating under the metal dome. Though it will always be possible to access Netflix by navigating to its icon, in just the same way you use other apps.
Yes, I know there are some button remapping apps. But I didn't want to be bothered with finding one that was a trojan horse, just doesn't work, or will stop working after some update.
Another button that annoys me is the microphone button. I don't like voice operated gadgets, they tend to be very bad at recognising what I say, you have to know what words it's listening out for, and it's another button that often gets accidentally pressed. Although you can configure the device to not allow the mike, it doesn't ignore the button. You get prompted with an allow the mike pop-up when you press it, interrupting whatever you were doing. I was tempted to neutralise that button, too.
If you don't like listening devices, you could always find where the mike is behind the mike hole in the front casing, and deliberately damage it.