Comment 49 for bug 704123

I'm using 15.10 and am experiencing similar problems with a Sierra Wireless MC7710 internal LTE card.
I _did_ save the PIN in the connection settings of network manager, but the apparently it's simply ignored.
The respective connection is set to auto-connect if available.
If I wait long enough at the login screen for the WWAN to initialize, I'm asked for the PIN, but unlocking fails because of insufficient privileges.
After login I can unlock my SIM after entering the PIN _AND_ sudo authentication.
This Bug is now open for almost 5 years, so although I'm not a dev I would be glad to do whatever I can to help fix it, finally!

Any suggestions on what type of information could help, or what I could try to narrow down on the cause?