We broke the story ... Usman and Covington -- who HATE each other's guts -- faced off at the Palms Casino Resort only hours after Kamaru beat Tyron Woodley at UFC 235 ... winning the welterweight title.

In the original video published by TMZ Sports in March, it was unclear -- outside of their disdain for each other -- exactly what sparked the fight.

However, the new video clearly shows Ali Abdelaziz confronting Covington -- who's in line at the buffet -- as Usman tries to hold Ali back.

It's clear Colby -- who almost immediately retreats and takes out his phone to record -- doesn't want to fight.

At one point, Abdelaziz charges and appears to knock Colby's phone to the ground ... before later throwing and seemingly landing a punch to Covington's chest.

The heated altercation lasts about 2 minutes ... but Kamaru never puts hands on Colby.

Covington previously claimed Abdelaziz threatened to shoot him during the altercation ... but if that happened, it's not evident in either video.

The bad blood between Colby and Kamaru goes wayyy back -- several years -- with the 2 fighters getting into it almost every time they're in the same room.

As for a fight in the Octagon ... Usman recently told us he was already in talks to make a Colby fight with Dana White and the UFC.

We reached out to Abdelaziz ... who declined to comment.