Keurig B-60 Single Service Coffee Maker Sticking...

Question

Hi My Keurig B-60 with the 3 different size serving buttons on top has developed a problem where the buttons are staying stuck in the down position which makes it virtually impossible to select the right size serving. I have used some alcohol or windex to free one up but this only works for a short time and then the problem recurs. Taking this apart is not all that straightforward as I started to do that. Any suggestions or thoughts on how to fix this one?Many thanks for the help.