They usually build re-shoots into the actors contracts and I would think with Star Wars they'd have an even greater buffer. They did a lot of re-shoots for Rogue One also.
The story going around is that the actor playing Han Solo first raised his concerns with how he was being directed to a producer who went to Kennedy and Kasdan. And that individual dailies were good but when looked at as a whole, it was bad. Compared it to Jim Carrey in the Mask, I think is what I heard. Sounds like the switch to Ron Howard was a good one.