10:04 AM PT -- Diddy sources tell TMZ, "Aubrey O'Day got her big break because Diddy and Bad Boy cast her in their show with her group, Danity Kane. Last year, when he reassigned his portion of the publishing to Bad Boy artists, an unprecedented move within the industry and which he did not have to do, not all artists signed an NDA, contrary to what she claims."

Aubrey O'Day claims Diddy was trying to buy her and other ex-Bad Boy artists' silence when he gave back their publishing rights ... which she says weren't worth jack.

We talked to the Danity Kane singer -- who was signed to Bad Boy Records in the 2000s -- as part of a new TMZ doc that'll be on Tubi Sunday ... 'The Downfall of Diddy,' which dissects the fallout after the raids on Diddy's homes, and the federal investigation that followed.

AOD provided some fascinating insight -- including the fact she knew what was up back in September ... when Puff gave all his old artists the rights to their music. The seemingly generous move came with lots of strings attached, according to Aubrey.

You'll recall ... Diddy made a big announcement at the time, saying all the old Bad Boy artists were gonna get what was theirs ... as it was the right and noble thing to do, etc.

However, behind the scenes ... Aubrey claims Diddy wanted the artists to sign NDAs as part of the deal, which would've muzzled them from speaking on their experiences at Bad Boy.

Aubrey says she didn't want to do that ... 'cause she sensed she'd be signing away her ability to speak -- something she finds incredibly valuable now, especially in light of everything that's been alleged against Diddy ... by Cassie and others, which he's denied. BTW ... Aubrey is the first and only person who publicly sounded the alarm for years.

There's also this ... Aubrey says the dollar amount attached to getting her publishing rights back was incredibly low. Take a listen ... it's astonishing, if true.

The other reason Aubrey turned down Diddy's offer for the publishing rights ... she's making a boatload of cash on her own, and doesn't need the pennies. Aubrey has dipped her toe into multiple ventures ... including OnlyFans, which has proven to be very lucrative.

She's got a lot more to say, all of which will be revealed in the doc, "TMZ Presents: The Downfall of Diddy", streaming on Tubi. Catch it then!