softwares that create layers the size of a canvas, create "empty pixels of information"
this information affects how everything works to that layer, meshing, automeshing, generation of atlas, the fact that it will not calculate correctly the space and if you have not a proper set of scale to 100% it can create a lot of holes in your atlas that may scale down your pieces
why this scale down is important in your problem?
you have a lot of not cleaned pixels around some areas, that the video is making even more visible than normal
and because you scaled down or because each layer information is huge, every problem is gonna be more visible and more noticeable
if the model is scaled down, those areas uncleaned will be bigger and bigger due to the antialing that happends when you reduce a picture in pixels trying to calculate areas around