This is not a BUG:hold shift and press crop,not respect the origin in some images,it means that some frames jump 1 pixel when playing animation.I think this is maybe because some images become odd pixels in width/height and some became even after croping.For example images with 93 pixel height and 94 pixel height have different origin y.
Some recommands:
1.using always odd or even in crop (startx,starty),width,height.
2.calculate the mini area contain every frames before crop,and make every croped frame same size.
Some feature request:
1.keyboard shortcut and button for,navigate to previous and next frame.
2.number editor for hotspot x,y.
3.Feature to select multiple frames and delete.