Preheats but drops temperature after that and won't maintain temperature

You may have a bad oven temperature sensor. Be sure to inspect the connection wiring to the sensor and you can ohm the sensor out. (should be around 1100 ohms at room temperature). If the sensor checks out good it sounds like the bake relay on the main board is failing . The part number for the oven control board is EBR73710105. I would recommend always replacing the sensor with any new control. The sensor for your model is EBG61305801. We could not find the exact service manual for your range, however I did attach a service manual for an LG LRE30 series range that is very similar . Unless removed, your model does have a tech sheet located inside a plastic sleeve on the back panel of your range.