I had the same issue (i.e., error check spots an issue in Step-By-Step View with 502A but that form is not listed in Forms view) and just figured out what you need to do. Go to Forms view. WHILE IN FORMS VIEW click the exclamation point/word "errors" in the top of the left bar. That will run an error check from within Forms view. A box pops up at the bottom right saying you have an error with Form 502A; click the "Delete Form" button at the bottom to delete form 502A once and for all. Then go back to Step-By-Step and file the state return electronically.
