OH! I just realized what is causing your problem! It's not a bug, it's caused by a misunderstanding of an animation timeline and how that effects export.
If you export keyframes only, it will export all key-frames, regardless of their position on the time-line, even if you have a key-frame at the very end of the timeline... BUT..
If you have a keyframe at the very end of the timeline, then what you're telling Spriter is you want that particular keyframe to be displayed for only 1 THOUSANDTH of a second, so you'd have to export the animation at a ridiculous 1000 frames per second for that exact key frame to ever be exported, and it would be lost in an ocean of way too many frames
If you're exporting based on FPS, then make sure any key-frame you want to be exported is actually displayed for long enough.. meaning if you are exporting at 24 FPS, then make sure there is 240 thousandths of a second or more AFTER the last key-frame! If you do this and your animation is not meant to be looped, make sure you turn off looping for that animation before exporting, so that last key frame isn't tweened with the first frame of the animation.