Here is the problem:
1) Connect a belt to the circuit network
2) Set some circuit settings for the belts (e.g., switch from "Enabled/Disabled" to "Read Belt Contents")
3) Create a blue print of this belt
4) Paste the blue print onto an already existing belt (that is not yet connected to the circuit network)
5) Bug: The circuit settings from step 2) are not applied to the existing belt. It will be connected to the circuit network, but it will have its default settings.
(Applying the blue print on an open area without existing belts works fine, here the settings are applied correctly)
Here is a simple example that shows the bug
Before:
After: