I think when the firewire chip is damaged all light flash; I think that's right.
I have shipped numerous U9 replacement chips (I am NOT suggesting your unit needs one),
and I SHOULD know the symptoms, but I do not.
By "cold" yes I mean the room is cold.
My Studio is about 60 degrees, this time of year, and my FW will not stay connected on boot.
Guys on the Tascam forum had complained that their FW had to "warm up", like tube gear.
I thought, and responded numerous times, that could not be right.
BUT, there is a Tascam service bulletin, its on my site, that recommends replacing one of the
firewire capacitors because they are temperature sensitive.
You say the firewire LED lights momentarily when you boot the 1884; right?
That sounds like maybe a cap issue in the power supply...
T