Can an mistake on Ds260 lead to a denial and would it be too late to make a correction after interview?

[Creed2 0]

I sponsored my parents a year ago for an IR5 and they had their interview last month, at the interview they were asked about previous US travel and were asked by the visa officer to provide all documents related to their entry and stay in America that was mentioned in their DS260, they didn't have the documents on them so were given a form 221-G white slip detailing them to mail those documents to the embassy. As my parents were collecting all the documents, I reviewed all of them and went over the DS260 again. I noticed that there was a question about whether my parents had a "visa revoked or cancelled" and they had marked 'No' based off their understanding of their case and the question however going over the old documents I noticed that in my parents diversity visa  petition denial from over a decade ago they were denied permanent residence for having not maintained their visa status for a brief period in 1995, at the time my father was on a student visa and my mother was a dependent and he was academically suspended for one semester however he immediately appealed that and transferred to another  college and his status was reinstated and was given an i20, he then transferred back to the first college after bringing his grades up after a semester and was given an i20. Now I'm not exactly sure if an academic suspension would mean the F1 was "revoked or cancelled" however it was reinstated right away under something called "nunc pro tunc" however years latter when his diversity visa petition was being processed he couldn't send the i20 for that semester as he had lost it but he did send i20s for subsequent semesters until he graduated and also sent OPTs however the officer deemed him out of status for that period and thus his petition was denied, although my parents had appealed the decision through their attorney and sent all supporting evidence, they got a letter the next year from the INS saying that they couldn't do anything on this case as their DV priority date had expired.

 

Now in hindsight I'm not sure if my parents should've ticked no for if they ever had their visa revoked or cancelled. Could this lead to a denial for 'misrepresentation' and permanent bar? Is it worth writing a cover letter along with the documents and 221g form, pointing this out and explaining what happened or is it too late for that? Also for those familiar with visa laws, does an academic suspension lead to a student visa being cancelled and does a nunc pro tunc ruling override that and that period?

Edited December 7, 2018 by Creed2