When copying a geometric network, if an associated BUILDERR table exists, it is not copied along with the network. The BUILDERR table is a user-managed table, and as such, it's not copied with the network.
The BUILDERR table can be copied in another operation, however, it can no longer be used to identify invalid features in the network. Copying the network to another geodatabase, breaks its connection to the BUILDERR table. To identify invalid network features, you must use the Verify Network Feature Geometry tool/command.
In order to use the BUILDERR table to identify and correct invalid features, you should make any edits to the network based on the BUILDERR table before performing Copy/Paste operations on the network.