It sounds like you might be having an issue with oxidation of the copper traces on the circuit board. Here is a pic of one of what that looks like….
If this is what you see in the area of the board where your bad buttons are, you can try and jumper the section of bad traces with wire & solder. I did attempt that with my bad remote but it only partially worked as the damage was too extensive. Here is what it was looking like…
Hope this helps.