I was wondering why the repost. This mistake probably had to do with the MangaPlus official post of chapter 4 as they seem to have happened in rapid succession. Maybe MangaPlus accidently took down 163 when they posted 4 since they only keep the three latest chapters available here and someone got into the "post a new one then remove the current minus 4 one" routine.
Edit: It appears that the same thing happened on
Hope You're Happy, Lemon. A new chapter 6 and repost of chapter 21. It looks like they keep more chapters up there though. Perhaps it's time based and not chapter count based?