GE double wall oven blinks "locked door"

Oven Repair (including Ranges and Cooktops)
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The top oven of our GE JKP45WW (circa 1996) double oven is flashing "locked door" and probably hasn’t worked in a few years (we just moved in). The bottom oven still works fine.

Could it be anything other than the upper latch oven assembly? From your website it is part WB49T10020. And how do I replace it?

Thanks