There are two objects in this image set that do not move in a straight line (but similar to each other).
Is this an effect of overlaying nearby objects (maybe in combination with earth rotation/movement and telescope pointing)?
Seen this once before but forgot to mention it here.
Yes, those are artifacts that are due to a general telescope positioning/pointing habit.
See here (+follow other links) for more details.
(The general consensus is that these artifacts are related to dust particles inside the telescope.)
The general related hashtag would be #artifact.
Mind you. this type of artifact can be seen in a lot of images.
(or ... specifically hash-tagging them would be somewhat similar to hash-tagging #stars.)