Oven not heating evenly during baking

I recently noticed that my oven doesn’t bake evenly anymore — cookies on one side burn while the other side stays undercooked. I’ve tried rotating the trays and checking the temperature settings, but the problem persists. It’s frustrating because baking requires precise temperatures, and I often have to throw away ruined batches. Has anyone figured out why this happens and how to fix it without replacing the entire oven?