GE Range (JBP95W T4) - issue with the oven controls

The oven doesn't heat up. I hear the relays engage for bake, broil, and convection, but they disengage 4-5 seconds later. There are no error codes showing. While the elements do get warm/hot from 4-5 seconds of power, the display remains for 30-45 seconds before disappearing. I did a continuity test for the elements and oven sensor and they all check out. I checked the power circuit to make sure - that checks out. I did some internet research and tried two (2) used control board: Neither worked as well as the original board. The first was DOA; the last one didn't engage the relays and the arrow keys didn't work. I'm not sure what to try next. There has to be a common problem somewhere. Maybe it's time to take it to the landfill...