I find it a bit hard to believe that there was no indication of an engine problem, except for a brief fire warning. That engine is pretty cooked !

From my experience circa 1979, and post incident the Captain of this flight stated, his first in over 30 years, the chances of a crew experiencing a real engine fire warning during their career would be very unlikely: post maintenance take off, multi, wide body, fire bell and lights, crew throttled back correct engine, warning stopped, fire test carried out satis, engine shut down and I think one bottle was fired as precautionary, returned to airport. Cause an HP air off take duct clamp failure inside the inter services area which was covered by fire wire sensor, but no fuel components in this area and no secondary damage.
Considering the earlier 2017 combustion chamber problems with this type of engine (and remembering the Manchester B737, JT8D, 22nd Aug 1985 cause) I am sure there should be a thorough investigation, even indeed, if it was just a loosening of the igniter over several flights!

I always thought igniters were wire locked in position.

Seem to recall the HT lead 'B' nut used to be, which effectively prevents the plug from rotating.

I'm pretty sure the igniters aren't wirelocked on the CFM56, so I'd be surprised if they are on the GTF.

The other igniters were wire locked…