From my experience faulty remote controls for TVs etc. can often be made to work again, especially if just some buttons don’t work. Firstly, it’s worth checking that the batteries are OK, and also that the terminals and compartment connections are clean. If they are dirty or corroded cleaning with contact cleaner fluid might work. If batteries are OK it’s necessary to dismantle the remote, however there is some risk of damaging it in the process. Accepting that risk I usually check if there are any fixing screws, but on more modern remotes two halves of the case have to be prised gently apart.

dismantled Sharp TV remote control

In this case the inside of the keypad and the circuit board required cleaning with tissue paper, nothing abrasive of course. I also used contact cleaner spray with no ill effects, but it’s not essential. On re-assembly it worked as new, although I didn’t get the positioning of the round pad correct at first. I’ve done this several times on some remotes, but with a lot of use the contacts may wear away. Apart from saving money by buying a new one, it’s one less thing to be discarded / recycled for about 20 minutes effort.