One of the founding members of Sublime has quit the band ... again.

Moments before Sublime with Rome took the stage at The KROQ Almost Acoustic Christmas concert in L.A. this weekend, drummer Bud Gaugh announced the show would be his last.

When asked why he was leaving, Gaugh said, "It's a long story" ... adding, "The story is that I'm gonna be a dad here again real soon, and I just wanna be there for my family."

But the tension had been building for a while -- TMZ broke the story, Gaugh stormed off the stage at a concert last month after hurling cuss words at the band's manager, Mike "Cheez" Brown.

We're told the guys tried to bury the hatchet ... but it seems things finally reached a breaking point.