Some couplers have a deeper cup portion of its dome...see picture
That designed in to hold the ball captive in the done during all maneuvers.
The latch holds the ball up in that cup portion of the dome.
Note that that portion of the dome (cup) has a lower hemisphere....meaning it has a smaller 'hole' than the balls dia
Think your ball us still in that front portion, or cup and will NOT allow the ball to drop out
Why I always block the trailer tires...unlatch...THEN BACK UP to move the ball out of the coupler dome cup...
As mentioned...maybe your latch is NOT getting out of the way...adjustment might or should get the latch out of the way
These pictures might help you see that 'cup' and how the latch Pawlenty has to get out of the way
excuse my fat finger typing n spelling...auto spell/fill on my smart phone begets wacky spelling
couplerlatch latch couplerpawl pawl dome