I also have a bit of electronic knowledge ( and perhaps a skill or two ) and have fixed a EPOI time with erratic behavior. There is what is commonly called a RC circuit inside for each time increment.
Simply put this is a capacitor (10 cent item) and resistor (another 10 cent item) together. Over time the capacitor can be a problem.
A competent techie at a fix-it store should be able to repair this quite quickly. I am just not sure if the capacitor bank (group of capacitors) would be available. Might be worth having somebody take a quick look and offer an estimate on the repairs.