CIE Fault is basically the control panel "crashing" and will require a power cycle to clear normally. You will also notice the time resets as well.
With faults like this it is best to isolate one thing at a time to diagnose the issue. Personally I would start by ruling out if it is the comms that is causing the issue in the first place.
FWIW all the CIE faults I have had in the past have been mains related, mains spikes, prepay meters/MCBs tripping out, noisy equipment on same CU.
Does the timing of the issue relate to any changes or new equipment?