The article pretty much says this:
- Executives at Disney aren't thrilled with the movie and have ordered reshoots to be done in July for about 4 weeks.
- Filmmaking team and studio expected additioning shooting. Actors were aware it may happen.
- The bar is set pretty high because of how well The Force Awakens did so they want Rogue One to be the best it can possibly be.
Some places I've read said this is all just a rumor while others say it isn't.