When I loaded into my Minecraft world I had to update it from 20w51a to 1.16.5, So what happened was when I loaded all the entities disappeared our pets and everything, also copper didn't exist at all...and I didn't make a backup because it always works when updating but when I updated there was some really dark stuff, that is because those spots were copper ore or copper and now we have to get new pets an everything.... 😞
MC-211624
1.16.5 Glitched Out
Resolved
Duplicate
0
Hello! This looks to be a duplicate of MC-211308. You have essentially downgraded a 1.17 world to 1.16. See @unknown's comment on that ticket for more information.
On a side note, a backup button will be introduced for downgrading worlds in a future version. 🙂