This thread, has prompted me to pull the original remote, which came with my LG set apart, to take a look. I soon after buying the set, bought a second remote, a 'magic' one. The magic has been trouble free, but the less used one, the power button had failed, and some of the other buttons were less than responsive.
Under the power button was some sort of grease, the rest of the buttons it seems were just dirty. I'll try giving the rubber keypad a wash in soapy water, and the PCB, a clean with electronics contact cleaner.
To get them apart, without damage, is not easy - luckily, I had a podger to slip into the gap, to force it apart. The podger, like a blunt knife blade, from a set of watch and clock repair toolkit. Having done all that, all the buttons work much, much better.