The source also claims Chmerkovskiy is now in "full blown crisis management mode."
"He realizes that he messed up," the source claims. "Vanessa isn’t afraid to stand up to him. She’s a very strong woman."
"He’s on thin ice so you can expect that he’ll be on his best behavior from here one out," the source adds.
However, a second source tells ET that Chmerkovskiy remains in good standing with the show.
"He’s one of the most popular pros on Dancing with the Stars," the source notes. “Maks and Vanessa are continuing to dance together and hopefully they’ll make it all the way to the finals. At the end of the day, Maks is always a professional. This is his job. He just needed personal time away not related to Vanessa.”
A DWTS spokesperson previously told ET, "Maks and Vanessa are returning to rehearsals and will be dancing together on next week's show."
On Wednesday, Chmerkovskiy tweeted that he took full responsibility for missing the show, though didn't apologize for his reported behavior towards Lachey.
"As you are all aware, I had to leave the show last week to take care of some personal issues," he wrote. "I take full responsibility for my absence... and want to apologize to my partner Vanessa. We are both looking forward to dancing for our fans next week!"