Thermador SCD302T double oven, approximately 20 years old.

Is extremely slow to reach temperature, using bake to 400 degrees.

Both bottom and top oven are slow to reach temperature, though bottom oven is slightly faster than top oven.

I've replaced the top oven bake element, which didn't help with the top oven.

Temperature indicator on oven control panel only increases in temp about 5 degrees every few minutes. A few months ago, it typically incremented in 25-50 degrees at a time.

The heating element appears to glow red for up to about 30 seconds at a time, and then the element turns off. I can hear the relay clicking when this happens. It seems it's turning on and off too frequently, with likely too frequent relay clicks.

The lower oven has only been infrequently used.

Any tips and confirmed replacement part numbers?

I do have electrical test equipment available.