We recently powered off our Tricity Sovereign Model 4638 to do some decorating. On powering up again the display flashes but part of one of the Zeros does not flash and the controller will not respond to any of the buttons we usually use to reset the clock.
We can use the top plates but not the ovens under this condition!
An old cooker this one and I’m afraid a new timer is required, they may possibly be obsolete now.
They did reach silly prices a few years ago and QER used to be able to repair them. You will need an engineer to do it though, and get the cooling fan checked for operation and dust fluff blockages.