oven started beeping constantly shotly after using it..and on display..said F7...the only buttons that respond are the start and the clear button...when either are depressed, the beeping stops but no oven functions work accept the clock, but within 45 sec, the f7 returns and the beeping starts again, i shut off breaker in an attempt to reset oven..the next day i turned it back on and all was good , then i decided to run the self clean mode and within 5 min...beep.beep.beep.. and the f7 code returned ?? can you help?...thnx scott in ct..