If there are lots of flowers, carpets and such, that are on your build, unless you have set the tickspeed to 0 using /gamerule randomTickSpeed 0 then they could get destroyed when you join the world.
If you are on a server you can do this via console, if you are on a single player world then you will have to do it before you load the world, or with the use of mods.
Copy paste not working because plants and stuff keep dying/dropping (copypaste) If you are trying to copy and paste something and the flowers (for example) keep dying or dropping, you can fix this by simply: //perf and turn everything off. Then /paper fixlight to fix the lightning.
Good to know: You can create a support ticket, describe your problem and, send proof of purchase so that you can be provided with the correct world download