How to update Rev rec created from JE, missing rev start/ end date, and forecast plan in bulk?

I have this client, who loaded JEs for midlife revenue plans during their migration. Their revenue field mapping are mapped at the SO header level, not at the line level. And therefore after revenue arrangement is created, you will see the date columns are missing. Somehow, later they are still able to create rev plan and had updated date properly on the actual revenue plans. But because the date on revenue element is missing, I am not able to generate forecast revenue plans. Is there any way to fix this other than going into the revenue arrangement and fill in