Two buttons - Minute minder and manual buttons do not work. They appear pressed down - maybe portion of end part is broken off. Before replacing them with new ones, how can I make sure of what the problem is?
Probably an accumulation of cooking grease and general filth. Carefully pull out the buttons and clean the shafts with a bit of cloth or apaper rowel and, using a cotton bud, the holes. WD40 seems to work OK but just use it on the cloth and cotton bud. Don't flood the thing!