Oven won't maintain temperature

[SIZE=3]My Frigidaire electric oven (model # FEB386WECH) will preheat perfectly, but the temperature drops steadily without reheating to maintain temperature. [/SIZE]

[SIZE=3]If I turn the oven off every few minutes, then reset the temp dial, it will keep baking (the heating elements will produce heat until the proper temperature is reached). If I don’t keep doing this the oven just steadily cools. [/SIZE]

I have replaced the temperature sensor, to no avail. Does anyone have another option to consider?