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.