Fast moving asteroid or cosmic ray artifact
IMHO this object does not look like a typical cosmic ray hit, so it must be an asteroid.
Is it possible to find the image set to the left of this one? Im not sure how this works, but It may show up there. Are images taken all at once ina big group? Its moving so fast, it woudl only show up if the area to the left was imaged in the 60-90 minute period after this one or simultaneously.
Mos cosmic ray hits are asymmetrical, and often have crisp edges because its going to set of a few pixels in a small area, but its usally an all or nothing thing. This looks round and has a soft focus edge like its a real object, not an artifact.
BTW first frame only VERY bright lower left