@Speiger I'm currently running Tekkit Legends 1.1.1 and I am experiencing the copper cable disconnect issue. However, it resolves itself after I disconnect from the server and then reconnect. So, as far as I can tell, the issue only occurs on the first logon after restarting the client. A relog fixes the issue.
Not really a huge problem for me, just thought I'd keep you updated.
Love the mod pack, by the way! Keep up the good work!
~Tech
UPDATE:
An 'Admin anchor' (hyped up world anchor) seems to also resolve the issue.