Rob Kardashian is currently "going through one of his mood swings," a source tells ET.
Despite some signs that all's not well between Rob Kardashian and fiancee Blac Chyna, Rob is still on board with their new E! reality series, a source close to the 29-year-old reality star tells ET.
As of Monday, Rob's deleted all of his Instagram posts from his official account -- including his previous snaps gushing over Chyna -- and a new report claims he has been skipping out on filming for their six-episode docuseries, Rob & Chyna. However, our source says this is "nothing new" for Rob.
"He is just going through one of his mood swings, which is common for him," the source says. "But he is still filming."
WATCH: Rob Kardashian Reveals Weight Loss in Rare Full Body Photo
"He goes through his dark periods," the source adds. "He gets depressed and doesn't want to really do anything, doesn't leave the house. It got better for a bit when he first started dating Chyna, but he's in a rut now. He'll snap out of it."
Last week, Rob and Chyna showed it was all good between them despite the split rumors, when they posted Snapchats of each other. Chyna's also still rocking her flashy engagement ring and spending time with his famous family, including her one-time close pal, Kim.
Rob has already returned to Keeping Up With the Kardashians, appearing in the current season in which the drama of his quick engagement to 28-year-old Chyna has been played out.
In one episode in May, Rob's older sisters -- 35-year-old Kim and 32-year-old Khloe Kardashian -- discuss Rob coming out of his shell for Chyna.
"Don't we kind of think it's a miracle that Rob -- who doesn't even show up to Christmas for the past three years, literally he wouldn't leave his room -- but the fact that now he's created a Snapchat; the fact that he wants to be so public blows my mind," Khloe said.
"She gave him confidence, more power to her," Kim acknowledged. "Even if there's been some drama ... If this is what it takes, then I don't care who he's dating. I'm so happy that he's just feeling better about himself."
Watch below: