If you're lucky and its not an actual fault, the fix for this problem can be really simple. It's just a case of pressing the minus (-) button on it's own to scroll through the volume settings for the timer.. hope this works!
If not, I'd probably gain access to the control panel circuit board, find the speaker that will be attached to it and see if it's blocked with dirt or grease.. would be interesting for future reference if you could let us know if the first suggestion worked or not..
Rupert, November 2018
