It sounds like your lattice strips are the wrong size. Sometimes the blocks don't come out exact and when one precuts the lattice according to the pattern, it will be the wrong size. It is better to cut the lattice in long strips and fit it to the block. It sounds like you will have to take the lattice off and resew it making sure the lattice is the proper length to your block.
Sorry, I hate to rip things out, but I don't see any other way. Just think of the little frogs sitting around saying "Rip-it, rip-it". It helps me.