AntcuFaalb said:

Anyway, do you have any idea why these changes are present? Also, are they changes? Errors? Recompositing?

Any recompositing are changes done to the film. The composite is part of the effect or basically you can say the composite is the effect. Whenever they recomposite, the timings and/or positions of elements become slightly different compared to the original compositing. Probably because they didn't even try to recreate them down to every little detail, the differences in timings and positions are mostly visible when comparing against the original compositing anyway, so I guess that's not on their priority list, sometimes they probably wanted it slightly different as well. Their primary reason for recomping is mostly to get rid of generation loss the optical compositing cause, built in dirt and matte lines. And back in the 90's when they first did it, it was also due to the many faded opticals that was on the unstable CRI-stock (Color Reversal Internegative).

The problem this cause is that many of these original effects were specifically done to look their best with this generation loss in mind. Filmmakers even took the generational loss that occurs in the steps from negative to print into account when creating sets and props etc. Seen on new hi-res transfers made straight from the negative, it tends to look fake in some instances.