KKMOON FY6800 pushbuttons

[fant]

Good morning;

I have the FY6800 from about three years and i have had no problems.
Now it is some months that the rubber pushbuttons are becoming more and more difficult to work, I have to push them hardly and very often when you push one button the display increase by 4 - 8 steps instead of one.

What is possible to do?

Thank you in advance