Common complaint about this model. Mine is the second of two (since the first was stolen and wrecked) and was FINALLY able to adjust things so the latch worked every time!
Get yours unlatched and see how the seat deflects as it closes just before it clicks in one or both latches. You will undoubtedly see deflection either to the left or right. Do whatever it takes to adjust that seat left or right to eliminate the deflection. The hinge up front is very stout and the holes can be Dremel or filed bigger or elongated to accomodate more adjustment.
I lubed the latches, the loops that went into the latches, lubed the cables, adjusted and sooner than later this thing would have to be broken into. Elongating ONE HOLE on the bottom hinge half SOLVED the stuck latch syndrome!
Some riders eliminated one latch. Some added a hidden pull wire. I actually like the design so figured finally how to fix it after the new wore off!