i2004 getting blocked!

[BlackCuervo]

Hi everybody, I am having a problem with IP phones, most of them i2004 Phase 1. They are connected to a BCM 400 3.7 and the issue is this: Suddendly, without a common reason, an IP phone becomes “blocked”. It is apparently idle, very normal, but if you try to press a key it doesn’t react. I mean, you can see the date & time in the screen as if it was working fine, but once you try to do something with it, you just can’t. Even, if you reset the Phone using the combination of: MUTE + Arrows (UP-DOWN-UP-DOWN-UP) + MUTE + 9 + GOODBYE, it doesn’t get restarted. So, the only way you can remove this “blocking” is disconnecting it and reconnect it to the switch.

Any idea of what could been happening?

Thanks in advance.