Tom Sandoval Lie Exposed by Schwartz After Timeline Mix-up at Reunion

Tom Sandoval can't catch a break from a single one of his castmates, including Tom Schwartz ... who's now revealed he knew about his friend's affair much sooner than Sandoval let on.

Andy Cohen got down to the nitty gritty with the "Vanderpump Rules" cast Wednesday on part 1 of the show's highly-anticipated reunion ... asking Schwartz when Sandoval told him about his affair with Raquel Leviss.

Schwartz says August, which seems to catch Sandoval by surprise because he'd maintained a different timeline. But, the folks at Bravo were quick to cut to a prior sit-down interview between Andy and Sandoval, where he says he told his friend in January ... a whole 5 months later.

The entire 'VPR' gang was sure to call out Sandoval on his lie. Lala Kent straight up asked, "What you guys didn't get your timelines straight before this?!"

As we reported, Sandoval got destroyed on Wednesday's episode for blowing up his 10-year relationship with Ariana and cheating with Raquel.

What's more interesting about the timeline mix-up ... in front of cameras, Sandoval had urged Schwartz to hook up with Raquel, despite the fact he'd already had sex with her -- and Raquel and Schwartz actually did kiss in August.

Sandoval tried making it clear, he and Raquel had only had a "one night stand" at that point, and later rekindled their flame. Strange turn of events, to say the least ... and there are 2 more parts of this reunion to come!