Gas oven is not holding temperature

My gas oven, Frigidare model FPGF3081KFM, does not always hold the correct temperature. It will always ignite correctly initially and come up to the correct temperature, but for long cooking sessions (half an hour or more) it will occasionally stop heating entirely. The interior will be cool to the touch despite being set to normal cooking temperatures.

I have already replaced the temperature sensor and the main (bottom) igniter element with brand new parts.

The gas burners on the stove top work correctly. I have not smelled unburnt gas at any point.

This may be a duplicate of these previous questions, but neither had a satisfactory answer:

Gas oven won't maintain temperature it is set on

Gas oven sometimes stops heating