Hello minegroasprilla,
Thank you for your post.
Am I right that you would like to delete the fragment from 00:08:02;07 to 00:08:04;14?
I've reproduced the issue with artifacts on frames of cutting place in the resulting file if delete this fragment.
Do you have the poor quality on the whole file or only on the cutting place?
I would like also to kindly ask you to upload the original input file to any file host service to be sure we have the same problems, as the file can be downloaded from YouTube with different downloading programs and this can affect on what video/audio information it has. You can use e.g. Google drive or Dropbox.com to upload it.
Thank you.