[cisco-voip] Phones going fast busy by selves

[Auralythic]

Good day, all,

We are an enterprise level network with CUCM 8.6 linked to CUBEs and
the SIP with a trunk linking to CCM 4 which is where all our phones
register save for a couple test phones in 8.6. We are in the beginning
stages of migrating completely to 8.6. Yesterday we had a strange
issue (also happened once several months ago). In the late morning,
phones began going fast-busy over speakerphone by themselves, without
any user intervention. This was primarily in 4 but one of the 8.6
phones also experienced this and the user of this phone was not in the
office. One of our staff heard the phone go fast busy after hers did
and walked into the office to confirm. This happened across several
departments at one site and users also reported seeing the "High
traffic, try again later" message. This particular staff also noticed
her phone's buttons ceased working, dialed a number by itself, and
generally went "haywire" before going fast busy as she was attempting
to use it at the time this happened. We made some minor changes in 8.6
the evening before this happened but like I said, this happened
several months ago as well (I am not privvy to any changes that may or
may not have been done back then). Any ideas or thoughts, any place to
start? These are not phones configured for auto-answer and I find it
very interesting that problems were reported on phones linked to both
UCM systems. Since this happened yesterday morning, there have been no
further reports of issues.

Thanks for anything you can toss out,

-Diana