The issue is most likely that you have a small piece of residual foreground not fully extracted on the top of the frame for images that do that. That is seen as part of the transparency “edges” and SPA aligns and scales to the residual pixels that are not extracted. It is probably a small piece that is hard to notice.
If you don’t want to fix the extractions then you can use the option in the SPA settings that says “Use Select Subject For Player Edges”, Then instead of aligning to the transparency edges it will run Select Subject and align to those edges instead. It will add a couple seconds per image but will fix the issue.
Just note, using the Select Subject setting isn’t what you want to use by default if you have equipment above there head or below the feet you are trying to align to. Say for example you have player in batting stances and you want to make sure to align to the top of that bat. Or if you have players holding a hockey stick below the feet you want to align to. Select subject is hit and miss with seeing sports equipment and in some cases it may not fully select see the bat or hockey stick. Then it wouldn’t align correctly to those.
So in those cases where you have sports equipment above the head or below the feet, the normal mode that aligns to edges will always work correctly, provided there images are cutout cleanly. That is why the select subject mode is not default.
In you case, the Select Subject alignment mode will work fine since they don’t have sports equipment above or below the person.
Anyway, let me know if the Select Subject alignment mode fixes it…. which I’m prettt sure it will.