Young Buck may have a little performance anxiety ... he's missed two court-ordered urine tests and has now been warned ... third time will NOT be a charm.
Buck -- who's on probation for gun possession -- has had a steady stream of drug tests since November when he got out of the slammer -- all with negative results. But he bailed on the 2 most recent tests.
Buck admitted in court docs he screwed up ... but his probation officer was pissed off and threatened to throw him in jail.
Fails To Pee On Schedule
Urine Trouble Now!
5/26/2014 12:25 AM PDT BY TMZ STAFF
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