I just fixed this issue a few months ago. due to age dust And other factors, the contacts tend to go. Pry the remote apart with a screwdriver, remove the battery, and pull out the circuit board. Depending on which version of the remote you have, you will see a separate plastic piece with a few metal contacts. What you're seeing is the "membrane." These contacts are supposed to be shiny and clean to allow proper contact when you press the button. Take a razor blade and gently ( I emphasize gently) scratch the underside where it sits ontop the circuit board. You will see it turn from dull to shiny as you etch away at all the years of use and dirt.
Now that you cleaned the membrane, you can reassemble the remote and test it out. If for some reason it does the same, check if you put the membrane back correctly. If you did and its still not working, disassemble again and clean the circuit board. To do this, use a toothbrush and pure acetone and brush away at the gold contacts under the membrane. Allow the board to sit in the sun for 30 minutes to assure it has dried properly. Reassemble and try it out!