Randy Gregory has a problem with marijuana -- that's what the Dallas Cowboys defensive end tested positive for during his last drug test ... league sources tell TMZ Sports.
We're told Gregory -- who's currently serving a suspension for failing previous drug tests -- was tested again at the end of last week ... and it came up showing weed.
Our sources say Gregory was notified of the result on Tuesday -- and has been concerned that the Cowboys could get rid of him. So far, we're told no decision has been made.
Before this, Gregory had reportedly failed 5 NFL drug tests. This is number 6.
One source close to Gregory tells us, "He has a problem quitting."
We've reached out to Gregory's rep multiple times.
NFL Network's Ian Rapoport broke the story about the failed test -- and pointed out that Gregory is now facing a full 1 year suspension, per the NFL's drug policy.