Universal Pictures is having an absolutely banner 2015, with record-breaking box office from a number of ambitious plays that range from big-budget reboots like Jurassic World to sequels to moderate hits like Pitch Perfect 2. But one of the studio’s biggest films of 2015 was Furious 7, a sequel that is currently the fifth highest grossing movie of all time with a worldwide gross of $1.51 billion. Obviously Universal wasted no time in putting together the follow-up, but while Chris Morgan has been busy scripting the New York-centric sequel, Universal is encountering some significant issues in finding a new director.

James Wan helmed Furious 7 and managed to navigate one of the most difficult productions in history, restructuring the entire movie mid-shoot to account for actor Paul Walker’s untimely death and result in a film that’s actually pretty solid. Universal had options on Wan to direct Furious 8 and Furious 9, but when he told the studio he wanted to direct The Conjuring 2 for Warner Bros. instead, they graciously acquiesced given how tough the Furious 7 shoot had been.

But in the wake of Wan’s absence, THR reports that finding a new filmmaker to take the helm has proved incredibly difficult. After Wan opted not to return, Universal went to franchise staple Justin Lin—who directed Tokyo Drift through Fast & Furious 6—to see if he’d be interesting in coming back, but he chose to direct Star Trek Beyond for Paramount instead. When that happened, THR reports that Universal went back to Wan with “life-altering money” as part of a new deal, but he once again declined.

Why the reluctance to return? Not only was it a difficult shoot logistically and emotionally, but THR suggests that working with star Vin Diesel was taxing:

“Sources say Diesel proved extraordinarily difficult. As a producer, he is said to have questioned even small details on elaborate action sequences, often holding up the complex production. He also was known to summon filmmakers to repeated late-night script sessions to make him comfortable with his character and dialogue.”

Both Diesel and Wan’s reps deny any on-set tension, and producer Neal Moritz goes so far as to say, “Obviously if there was any issue, we wouldn’t be making the eighth [film] with [Diesel] right now.” The studio is currently in the midst of casting a wider net, approaching Non-Stop helmer Jaume Collett-Serra (who’s unavailable) and both experienced action directors and relative newcomers. THR says some at Universal fear that Diesel will want to direct an installment of the series at some point, while another source says that prospect doesn’t interest Diesel. Regardless, he remains involved as a producer on the series and must be consulted on director choices, though he does not have veto power.

Wan was a newcomer to the action genre and made the transition quite well, so I imagine the studio isn’t focused solely on those with experience crafting set pieces. But as the film’s April 2017 release date approaches, they may be veering closer to those at least nominally versed in the action genre due to what could become a very tight schedule.

The Fast & Furious franchise has grown into a fascinating beast, toeing the line somewhere between action soap opera and cartoon, so when it comes to choosing a filmmaker to take the helm, a variety of choices seem appropriate. Personally I’d love to see John Wick directors Chad Stahelski and David Leitch bring a grounded, fist-fight-focused approach to the franchise, but alas they’re busy with John Wick 2 at the moment. Given Wan’s horror background, I’m also fascinated by what The Babadook director Jennifer Kent might do with the franchise.

What do you think, readers? Who would you like to see direct Fast & Furious 8? Sound off in the comments below.