Replaced the display board after it had repeated erratic behavior when oven door was open (especially at temps above 400F, but slowly trending downward). This cured the problem completely. The display board is located directly above the oven door and gets a blast of heat when the door is opened. Saw code E011 displayed among several others before the repair.
The new board also brightened up the numeric display considerably. It looks like new again. My guess is that the board's power supply had deteriorated due to repeated heat stress causing the vacuum fluorescent display (the blue-green numerals) to characteristically appear weak. This probably indicates the display board itself was hanging on the bottom edge of its operating voltage range and a blast of heat was all it took to send it over the brink. The oven had been in use for 6 years (since 2016).
I am extremely pleased with the repair. The only tool I needed was a T20 Torx screwdriver to remove the four-panel screws and a set of hefty neddle nose pliers to bend and straighten the board retaining tabs.