We have a De Dietrich induction hob.
This is playing up, If we use the two hot plates on the right it works fine, however if we try to use all four hot plates it does all sorts of stupid things. Normally they all cut out, or some cut out. Does anyone know the reason for this?
Is it worth getting an electrician to look at it or just buy another unit?

a lot of electric hobs have crossovers in the wiring connections, so that i can be connected to more than one phase. When its wired single phase, a U shaped piece of metal links L1 and L2. If one of these was dodgy then that would explain why they are playing up in pairs?

Certainly worth a look at the connections, but make sure its safely isolated.