Doctor Strange in the Multiverse of Madness, Benedict Cumberbatch-starring sequel to Marvel Studios’ 2016 Cinematic Universe installment, is getting some major reshoots.

In what sources describe as a “significant” production, the new shoot, taking place in Los Angeles, comprises both “additional photography” and “reshoots.”

How significant? Insiders say that Cumberbatch and company are undertaking six weeks of shooting, if not more, working six days a week.

Sam Raimi remains as helmer, and Loki head writer Michael Waldron is still on board writing the new material. It is unclear what actors in addition to Cumberbatch are on the call sheet. The crew involved is familiar with the Marvel method and worked on recent pickups for the upcoming Spider-Man: No Way Home and additional shooting for next year’s Oscar Isaac series Moon Knight.

One source downplayed the severity of the shoot: “Even while in the middle of production, Marvel is scheduling you for more shooting,” this person says, adding that the size and complexity of Marvel movies often necessitates additional photography.

“We’ve had bigger reshoots on other MCU movies,” another insider says.

However, other sources raised their eyebrows at the six-week time frame. “They’re here until the end of the year. That’s like a whole other movie,” says one.

Several factors appear to be driving the return to production. One insider says about two weeks are dedicated to principal photography that wasn’t completed during the initial, U.K.-based shoot due to what is described as actor availability issues. The insider also dismissed concerns that the reshoots were related to retooling the story.

Another reason for the shoot concerns compensating for COVID-related production slowdowns that affected the U.K. production.

Those slowdowns reared their head October 18, when Marvel and Disney unexpectedly announced the pushing-back of Multiverse of Madness from March 25, 2022, to May 6, 2022. Thor: Love and Thunder, Black Panther: Wakanda Forever, The Marvels and Ant-Man and the Wasp: Quantumania hopscotched backward into new dates as well.

First announced at Comic-Con in 2019, Multiverse of Madness is an ambitious project for Marvel, with one aspect dealing with alternate versions of fan-favorite superheroes, much in the way that recent Disney+ series What if …? has reimagined Marvel mainstays.

The movie had faced several challenges.

Doctor Strange director Scott Derrickson had co-written a script and was due to direct when creative differences led to parting of ways in January 2020.

Raimi and Waldron were brought out to, as one source says, create a whole new movie, on an accelerated timetable to boot.

Multiverse of Madness started production in the U.K. in November 2020 but paused in January 2021 due to the worsening pandemic. It then restarted — and ostensibly wrapped — in the spring.

Still, despite story concerns apparently playing a minimal part in the new shoot, it is evident that working in the multiverse requires Reed Richards-level thinking. Half the time, a Marvel movie has to tie to past movies while setting up future movies, and increasingly, TV series.

Despite the major shoot underway, the mood with cast and crew is not downbeat. “There is a pervasive enthusiasm,” one source described.

Cumberbatch spoke about the reshoots on Jimmy Kimmel Live! where he was asked if he knew what the reshoots were going to be.

“Like everything with Marvel, it comes in fresh, pretty much, most mornings,” Cumberbatch said with a laugh when questioned. “It’s really exciting, and the film is shaping up to be something special.”