siemens hbs50550b/02 oven

when the customer is cooking things like roast potatoes steam builds up in the oven and apparently the clock starts to flicker and makes a shorting/crackling noise, it did the same whilst it was under gtee they replaced the pcb which had blown shes called me in to try and avoid it doing the same,i checked everythig that i could and placed a tray of water in on full temp to create some steam but as usual it worked ok, all i can guess is that the steam is condensating on the pcb causing a problem, cooling fan was working.has anyone else had this problem?

cheers paul