Meanwhile, Lord and Miller, the exceptionally successful team behind The Lego Movie and 21 Jump Street, were chafing, too, according to a source close to them. There were "deep fundamental philosophical differences" in filmmaking styles, this person says, and the directors felt they were being given "zero creative freedom." They also felt they were being asked to operate under "extreme scheduling constraints" and "were never given enough days for each scene from the very beginning."

Shortly after the shoot in the Millennium Falcon, on June 20, the world learned that Kennedy — with the backing of Disney studio chief Alan Horn — had taken the extraordinary step of firing Lord and Miller. Obviously, Kennedy knew this would set off a storm of publicity that no one wants or needs in any movie — especially one in the Star Wars universe, where every move is closely watched by a gigantic audience with a sense of ownership. It's rare and undesirable enough to fire any director. Firing established players like Lord and Miller, who have a fan base ready to give them the benefit of any doubt? That shocked Hollywood's most seasoned veterans.

Anxious to avoid an outright rupture, Kennedy is said to have made attempts first to support and eventually to supplant Lord and Miller to some degree, as happened with Gareth Edwards on the troubled Rogue One. In that case, screenwriter Tony Gilroy took on significant duties with the cooperation of Edwards; in this case, sources say, Kennedy attempted to cast Kasdan in that role. Unsurprisingly, Lord and Miller were less accommodating than Edwards, still a novice, had been. Lord and Miller declined to comment, as did Kennedy.

As soon as shooting got underway, insiders say, it started to become clear that Kennedy’s stated intention of hiring directors who would put their own spin on Star Wars movies had led to a mismatch. Some insiders say that while the talent of Lord and Miller is undeniable, nothing in their background prepared them for a movie of this size and scope. These sources say they relied too heavily on the improvisational style that served them so well in live-action comedy and animation but does not work on a set with hundreds of crewmembers waiting for direction.

“You have to make decisions much earlier than what they’re used to,” one of these sources say. “I don’t know if it’s because there were two of them but they were not decisive.” Production department heads began to complain. While the pair appeared to listen when told of festering problems, this person says their approach did not change.

But the source close to Lord and Miller acknowledges they have always worked in an improvisational style and not just to add comedic elements. "They collaborate closely with their actors and give them creative freedom that, in their experience, brings out the actors' best performances," this person says. "Lawrence Kasdan would not allow this and demanded that every line was said word for word. To appease him and the studio, Lord and Miller would do several takes exactly as written and then shoot additional takes."

Matters were coming to a head in May as the production moved from London to the Canary Islands. Lucasfilm replaced editor Chris Dickens (Macbeth) with Oscar-winner Pietro Scalia, a veteran of Ridley Scott films including Alien: Covenant and The Martian. And, not entirely satisfied with the performance that the directors were eliciting from Rules Don't Apply star Alden Ehrenreich, Lucasfilm decided to bring in an acting coach. (Hiring a coach is not unusual; hiring one that late in production is.) Lord and Miller suggested writer-director Maggie Kiley, who worked with them on 21 Jump Street.

When Kennedy felt that these measures did not get the production on track, she asked Kasdan to come to London. Kasdan is said also to have been unhappy with the limited shots and displeased that Lord and Miller were calling out lines for the actors to try from behind the monitor rather than sticking with the script that he had written in collaboration with his son. (Lord and Miller had input on the script before shooting began.) “As a writer, producer and part of Star Wars world, you get on a plane when that happens,” says a person with knowledge of the situation.

But Lord and Miller were not prepared to have Kasdan become a shadow director. With an impasse reached, Kennedy finally pulled the trigger.

Stepping in to replace directors who have been fired is not something that many filmmakers would want to do. Ron Howard is probably one of the few who could and would — at least, in this particular set of circumstances. Insiders say he was concerned about how Lord and Miller would react and has been emailing with them; another source says the two have been “very supportive, very elegant.” Howard arrives in London on June 26 and shooting, which began in February and was supposed to be completed in July, will continue into the first week of September as Howard captures new material. Still, an insider says much of what Lord and Miller shot will be “very usable.”

How credit will be determined is up to the Directors Guild of America. What will happen next for Lord and Miller isn’t clear, but they are in demand and have an open berth waiting for them to direct The Flash for Warner Bros., if they chose to take it. (They had left that film for the Han Solo movie but could return.)

While Kennedy declined to comment on the episode, just a year ago, THR did a Q-and-A with her that sheds light on her thinking. Kennedy discussed her belief that within major franchises, it is possible to “take artistic license and creative risks.” She added, “If all you're doing is playing it safe — trying to make the same movie over and over again — that's when the audiences say, 'Oh, this is just a moneymaking machine.’ But if it's genuinely in service to the art form, then the franchise concept is being used in a way that's exciting.”

But at the same time, Kennedy — speaking in the context of hiring young, relatively untested directors (as opposed to established filmmakers like Lord and Miller) — said these choices were “instinctual.” And she continued with a statement that seemed, perhaps presciently, to address what may have gone awry on the Han Solo movie: “One of the things I've come to realize since I've been in this position of keeping Star Wars going is that in addition to looking for somebody who can creatively have an impact, you're really looking for leadership skills. No one steps into these big movies without being able to genuinely lead the charge with hundreds of people and [handle] the relationship with the studio. That's a very difficult thing to do, and you don't know [a person can do] that until you get to spend time and watch somebody operate.”

There are some in the industry who see an emerging pattern suggesting that Kennedy’s appetite for creative license and risk-taking will have to be curbed. Josh Trank was dismissed from the second Star Wars stand-alone film before he even started based on problems with Fantastic Four; Edwards, who conceived of Rogue One as a dark war film, was shunted aside; and now this. For all the talk of hiring filmmakers with their own vision, observers say Kennedy and Disney may be learning that the franchise is defined by a particular set of parameters. “All of the films have been 'troubled,'" says a top executive at a rival studio. “J.J. [Abrams] was powerful enough to push back on an unrealistic start date [for the first movie], but that was a tug of war. The last one was reshot by Tony [Gilroy] for months and now this? This is a systemic problem.”

But an insider argues that Rian Johnson (Looper) shot Star Wars: The Last Jedi, set for release in December, seamlessly, proving that the right director can execute without major interference from Lucasfilm. The search for new and interesting filmmakers will continue and for many, perhaps, the siren call of Star Wars will be impossible to resist.

On the Han Solo movie, a high-level insider says Kennedy and Disney "were hoping for a meeting of the minds [with Lord and Miller] that never came." But if had Kennedy fired them earlier, another source says, “People would say, 'Why the hell didn’t you try to work it out?’ You’re damned if you do and damned if you don’t.”

June 26, 4:15 p.m. A previous version of this article stated that the crew of the Han Solo spinoff broke into applause following the announcement of Ron Howard as director. In fact, these sources say the applause came at the end of the meeting in which the departure of Lord and Miller was announced and they were informed a new director would be arriving. These sources say the mood at the meeting was somber but there was applause "in support of the movie" (not in support of Lord and Miller's departure).