We haven't had a lot of problems with LAN cables that I'm aware of. We are not using the cables provided with the phone, rather I think we used Panduit for all of our cabling.
Second, we are using power over ethernet out of the closet. We have lost a couple of the powered switches, which obviously knocks down the phone. The phones should come all the way back though when the power comes back. One thing to keep in mind is that if you change the password on the station in the switch or using remote access, the password in the phone is still the original, and that is the password that the phone will try use if ever reset. Knowing that, we have found that we have to log the phone off and back in if we do change the password. Otherwise the phone will get stuck at the password prompt, and our users have no idea what to do. We do not give the passwords for the phones out to users to discourage them picking a phone up and moving it.
Not sure that this was much help. My guess is that your option number 2 could very well be the culprit, and if so, making sure that the passwords all match up should help.