This has happened a couple times already.
First off, chunks change back to a previous state
Example: Dungeon forgot it had been raided
Second: Chests decide to wait 5 seconds before opening
Third: Buttons decide you're not the boss anymore
Fourth: Downloading materials screen pops up for a while
(Don't respond)
Fifth: Chunk loading becomes horribly slow
Sixth: Massive frame problems
Seven: World-backup time
This is a horrible problem and is probably a duplicate post.
This ticket is invalid as it relates to a modded or 3rd party client/server.
Any non-standard client/server build needs to be taken up with the appropriate team, not Mojang.
Any plugin issues need to be addressed to the plugin creator.
This site is for addressing issues related to the base unmodded Minecraft.