Hello My name is Ian ~ I am not on the site constantly so please be patient whilst waiting for responses to you queries
How long has the oven been fitted and and if for some time is this something that has just started to happen?
OK how handy are you with a multimeter?
OK well I think it would be a good idea now to get someone to check the wiring within the cooker. Usually when you get control problems like this it is because something has shorted out and the power is able to by-pass the switches. If you need an engineer to come and check I can give you a link to a association that has listings of local engineers. Or perhaps you have someone who is an electrician who can check for you? I don't think that it would be a good idea for you to proceed further without the necessary electrical experience or training ~ Ian