Are Maks Chmerkovskiy and Vanessa Lachey fighting during Dancing With The Stars rehearsals? According to insiders, there's a serious chemistry issue and it's unclear how it will affect the DWTS duo for the rest of the season.

“There’s a big chemistry issue,” an insider told People. “They both have big personalities and that’s not always the best recipe for a good partnership.”

Last night, after Tom Bergeron said ABC would dedicate the show to the Las Vegas victims, Erin Andrews told the audience that Maks would be taking the night off for personal reasons.

Maks And Vanessa Aren't Getting Along During Dancing With The Stars Rehearsals Sources say Maks and Vanessa aren't getting along behind the scenes.

“Maks is dealing with a personal issue so Alan [Bersten] is stepping in and dancing with Vanessa tonight,” she said, referring to a professional dancer who was previously paired with Debbie Gibson. Debbie has since been eliminated.

Nick's wife had previously been one of the favorites to win this season. Jordan Fisher, Lindsay Arnold, Lindsey Stirling, Mark Ballas, Nikki Bella and Artem Chigvintsev have also been early frontrunners.

"Maks and Vanessa are returning to rehearsals and will be dancing together on next week's show," a spokesperson for the show told Us Weekly. But will the dancing team be able to overcome their tension?

Vanessa and Alan Another professional dancer, Alan Bersten, filled in for Maks this week.

"There is a lot of fighting going on behind the scenes," a source told Us. "They're playing nice for the cameras but both are miserable paired with each other."

This isn't the first time Maks has had an issue with a partner. His disdain for Hope Solo was hardly a secret at the time. “We didn’t have a good time on the show and it’s been highly documented,” Maks has said.

“She’s not somebody I talk about. I don’t like her and that’s the end of it.”

Do you think this will affect Vanessa Lachey's chances of winning DWTS? Let us know your take in the comments section below!