I just bought a house, appliances included. The oven is a Whirlpool Accubake RF265LXTY3. We have tried to cook several times and it is hit or miss.
It seems like if I cook a pizza around 350 that takes 15 minutes or so, it cooks fine. If I try to cook a frozen casserole or pot pie for 30 minutes or more (350-400), it never gets done. Even frozen fries have spent an hour in the oven and never fully cooked. I tried a brisket on 240 for 8 hours with a temperature probe and the internal meat temp rose but after a few hours (4-5) slowly declined, even when I cranked the heat up on the oven (and left for 2-3 hours). I have heated it to 400 with my smoker temperature probe hanging from the middle rack and it gets to 390-400 range.

Bake element- 24 ohms resistance
Broil element- 17 ohms resistance
Oven temperature sensor- 1070 ohms resistance

TL/DR- Short cooks (15-20 min) cook fine, even at 400. Long cooks (over 30 mins) at varying temps, food gets warm but never cooks/browns.

Its like my oven gives up. Any ideas?