When using the /clone command to copy blocks, they don't update after being cloned. Examples of this are:
Pistons staying extended even if not powered
Fences connecting/disconnecting when they shouldn't
Redstone lamps staying powered wrongly
How to recreate:
1.) Place a block that changes its state based on the blocks next to it (two fences, for example, connect when next to each other)
2.) Use /clone to clone only one of the fences
3.) The cloned fence will still have its "connected" part, even if the area it's cloned to doesn't have a block it can connect to.
Linked issues
Comments

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We're tracking this issue in MC-31100, so this ticket is being resolved and linked as a duplicate.
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Isn't the definition of a clone a quasi exact copy of something else?
It makes absolutely sense to me that no update of its blockstate would occur.
As a mapmaker, I personally would be rather upset if I would clone a sophisticated blockstated thing (that I e.g. accomplished with a debug stick), and when I want to clonse it to another part of my map, it would reset its blockstates, and I'd have to redo all that blockstating debugsticking again.