de dietrich oven fw5847 e32

hi guys,
After an hour and a half of cooking at 190 on fan assist, the entire oven cuts out, display also. I’ve replaced the board, probe, lock assy. the cooling fan is running fine too. basically its obviously overheating or thinks its overheating but i’m unsure what controls this. there is a limiter stat but it sits at the base of the small lower oven. After 15 mins the oven comes back to life
any ideas??
cheers