Kemore gas range

I have a Kenmore gas range. It has the glow bar type ignitor. I have changed it already trying to fix the problem. You can turn oven on, ignitor glows, but oven does not light. If you turn on one of the top burners, as soon as you open the gas flow with the burner knob the oven lights instantly. Then during cooking the oven will go out and temp falls. I’m guessing when it reaches temp and flame goes out, oven will not start back. Ignitor will be glowing the whole time. Any ideas? Safety valve, regulator?