'Dancing With the Stars' couple allegedly 'fighting a lot' behind-the-scenes

There's drama brewing behind-the-scenes on "Dancing With the Stars" this season.

On Monday night's episode of the hit ABC dance competition show, host Erin Andrews revealed that Maks Chmerkovskiy wouldn't be competing this week because he's "dealing with a personal issue."

SEE ALSO: Dancing with the Stars week 3 recap: Which couple should go home?

Pro Alan Bersten danced with Chmerkovskiy's partner, Vanessa Lachey, instead. Bersten was eliminated with Debbie Gibson last week.

According to sources close to "DWTS," though, Chmerkovskiy's "personal issues" are directly correlated to his contentious relationship with Lachey.

"They've been fighting a lot," People reported. "There's a big chemistry issue. They both have big personalities and that's not always the best recipe for a good partnership."

Adding to the potential drama would be the presence of Lachey's husband, Nick, who is also competing on season 25 of "Dancing With the Stars." Not only that, but he's paired with Chmerkovskiy's real-life partner, wife Peta Murgatroyd.

The insider alleges that -- though it's unclear where it truly stems from -- the bad blood between Chmerkovskiy and Lachey could end the "DWTS" pro's time on the season for good.

"I wouldn't be surprised if Maks doesn't return as her partner for the rest of the season," the source finished.

Though pros have been permanently sidelined in the past due to injuries, this would seemingly be the first time that a pro stepped down from the competition because of inter-couple tension.

RELATED: Odds of every couple winning this season of "Dancing With the Stars":

More from AOL.com:
Bill O’Reilly calls Las Vegas shooting 'the price of freedom’
John Cena shares steamy kiss with Nikki Bella on stage after sexy 'Fifty Shades'-inspired 'DWTS' routine
'Flip or Flop' star Tarek El Moussa was at the music festival where the Las Vegas shooting happened