Yes - the gasket needs to be replaced. I'm not sure exactly why that would have happened. Have you had a similar experience before or just since you had the gasket replaced? When you locked the lid, did it seem to fit smoothly or is it catching on something? Here are a few more thoughts:
How well did you clean the gasket and canner after using it? Some food particles may stick to the rim of the pot, including grains of salt, spices, oil, fats, and other food particles. If you don’t clean it, the food will stick to the gasket and may tear it as soon as you open the lid the next time.
Did the pressure canner ever run dry? The internal heat can easily damage the gasket material.