I am guessing the engine was a RR trent - 700 0r 800 can't remember.
This engine on the A340-500/600 has had a horrible record on this airframe.
Rumour has it the EK have had over 20 engine changes of this type in the previous 12 months on their Airbus fleet.
At present SIA have numerous RR powered 777 grounded due to lack of engines.
I am guessing what you were seeing was the erosion/failure of the HP compressor as this seems to be its' archilies heal at the moment.
Usually causes no problem during the flight except for a small parameter shift in egt or N3 vibes and that the engine won't start after the next transit if the shift isn't noticed....
As apaddyinuk mentioned, You should have brought what you were seeing to the attention of the CC to get it looked at next port...
