Even after the great tip [scratch off the paint] by fatbloke, my OK button on my remote was very poor. So I opened it up to see if I could fix it. There was some moisture inside under the volume and channel rocker keys, but apart from that not much [I didn't have any issue those keys!] I cleaned the circuit board and the keypad's underside with isopropyl alcohol on cotton buds. And I was amazed to find it fixed my remote. Even while cleaning it I really didn't think it was going to work. But work it did and the difference is astonishing. I used to have to ram the OK button into the remote, and even then it was touch and go. A bloody nightmare if I had to enter text like when renaming a file. And once fixed I also realised I had the same problem with the power button. I took some photos and I've posted them to help any one else who might want to do the same. I found the top and the bottom covers are clipped together. The top cover has little female recesses that receive the bottom cover's male clip heads. I managed to break at least three of the top cover's female recesses when prizing it open. It seems to be made from a relatively brittle plastic. Thankfully when I closed it up there is still enough good clips to hold it securely. Update: I came across a tip [after I had opened mine using shop loyalty cards ] that recommended guitar plectrums to pries it open with which seemed like a good idea.