we have had some problems with that this year, what we found is that the nylon strap that holds the lid gets caught in the pivot point and wont allow the latches to close fully
My 05 roadking did the same thing, there actually is an adjustment procedure in the owners manual, You acutally bend the little fingers to tighten the latch, works great now. IF you cant get it stop at a dealer, should take them about 30 seconds.
I've found that if I put too much stuff in the bag, to the point where it expands a little, it won't latch properly. Rearranging the load usually helps.