Dear Orestes,
A possible aerodynamic cause could be ice on the back side of the front end core engine compressor blades, we don't know if this crew, or the BA38 crew, even had the engine anti-ice system "on" ?
Even if they had it "on" it does not work when power is at idle from top of descent (as was the case with BA38) to 2000 or 600 feet.
This kind of ice can/will cause the engines to "hesitate" but will long be gone,
when you start looking for it, if the airport temperature is well above freezing.
AAIBs conclusion, that (birds and) ice are ruled out, is way premature.
Read more about engine icing here:
www.whistleblowers.dk
Enjoy your reading and thinking.