I also did not have 502a in my list of Forms when I clicked the Forms icon in the top right.
Instead I had to, while reviewing after not being able to submit, was on the step when it highlighted in red the 502a section A boxes, was to THEN go into forms (from the top right Forms icon) and 502a automatically popped up, and I hit Delete Form at the bottom, and was able to continue on to submit.
