NT-mode L1 state machine issue

Hi again!

Unfortunately, I'm not sure if that topic has ever been discussed here.

There is an issue where a port operating in NT-mode can lock up.
Either L1 stays down (according to lcradmin state) and there's no way to
bring it up again. Or, more interestingly, it can happen the other way round
i.e. L1 is reported as up, even if nothing is connected to that port.

I have no distict way to reproduce the issue. But if you unplug and replug a
terminal several times, there's a good chance to hit it.
Once you've got it, the port stays dead.
Sometimes the situation can be resolved by removing and reloading the
hfcmulti kernel module. Sometimes there's no way around a reboot.

The reason I come up with it now it that I just found out that it doesn't
only happen on BRIs, but on PRIs as well.

Unfortunately I'm not sure where I shold start looking for clues. So any
hints are much appreciated.

  Greetings,
    WIMPy