Why are my videos rejected for quality reasons?

the label wont tell you which one it is, adobe only says the review found "one or more technical issues". since some of yours got through, i'd put one refused original next to one accepted original and compare the technical side first (the originals, not the resized copies you posted)

what adobe checks against lists : fps has to be 23.98, 24, 25, 29.97, 30, 50, 59.94 or 60, and the frame size one of their 11 (2560x1440 for example isnt one). no audio track at all, even a silent one. h264 or prores to be safe, 5 to 60 sec. upscaled footage is refused too, and so is uhd exported into a 4096x2160 frame, because you get black bars on both sides

if the refused ones match the accepted ones on all that, then its something those lists dont catch, maybe the motion like you think. hard to judge that from resized copies tho

Carefully read through the 7-part Video Requirements in Contributor Help, starting here: 

1. https://helpx.adobe.com/stock/contributor/submit-your-content/submit-videos/video-submission-overview.html