Thanks for your reply, Gene.
Actually (and this is a little embarrassing), since I posted my question I noticed on p.8 of the “Service Data Sheet” the instructions for “Adjusting Oven Temperature”. I see that indeed my “Step 4" was to press Cancel. (Actually, the procedure in the manual lists 5 steps, exactly as you posted.)
The important point is that, once the calibration is finished, the oven is shut down (not returned to baking mode).
So here’s where I am now: The oven in question (which is used 95% of the time) seems to take a bit long to reach 550F. But also, even with a 35 deg. nudge, it still seems to only be able to reach 510F or so. I’m beginning to suspect the element itself. I wonder if you agree w/ this suspicion, and whether you think a reasonable test might be to temporarily swap the lower oven’s element and see if it can get to 550F (as a confirmation). Any thoughts?