Fox has halted production on the studio’s Queen biopic, Bohemian Rhapsody, due to the “unexpected unavailability” of director Bryan Singer.

Rami Malek is starring as the legendary frontman Freddie Mercury in the movie that had been filming in London.

“Twentieth Century Fox Film has temporarily halted production on Bohemian Rhapsody due to the unexpected unavailability of Bryan Singer,” reads Fox’s full statement. The crew received force majeure letters today, says one insider.

Sources tell The Hollywood Reporter that Singer failed to return to set after the Thanksgiving holiday break, leaving producers nervous about the state of the production and talking about potentially replacing him.

In a statement to the BBC, a rep for the director says his absence is due to “a personal health matter concerning Bryan and his family.” However, sources say that filming on the biopic has not been easy. For example, insiders tell THR that producers and his star had grown tired of Singer’s behavior, which saw him routinely show up late to set. Another source has said that a cinematographer had to step in and direct during a previous “non-showing.”

This is not first time that Singer has disappeared during a production. He momentarily vanished during the shooting of X-Men: Apocalypse and during Superman Returns.

Bohemian Rhapsody is set to hit theaters on 12/25/18.

This article originally appeared on The Hollywood Reporter.