Better to show it with gif, since it's kinda hard to describe this.

Hopefully gfycat will load fine, since imgur not allowing a long gif,
If you can't view gfycat, let me know where to post this.

Link :
https://gfycat.com/similarwarybichonfrise

Explanation :
When copy paste circuit setting on top of existing miniloader entitites, (using Ctrl+C; Ctrl+V) .
Some miniloader just ignore the setting/paste circuit condition.
There should be steel leftover in the left chest.
But three miniloader just ignore the circuit condition and keep unloading.
Also, (i forgot to record in the above link); The circuit setting itself is being pasted, but they were ignore, as if no circuit setting were being applied to them.

In the later part, the circuit setting were paste/build by blueprint ghost/bot, and the setting were properly being follow.

I think what happen is, the setting were only being pasted to one of the hidden inserter entity, not both .
Because in another test, i see one lane still unloading stuff, while the other lane is stop unloading.