From reading the AAIB reports, it would seem every component they've tested so far does/has work(ed) according to design parameters. This includes the integrity of the fuel supply system from both tanks.
We have symptoms of fuel starvation to the power units, cavitation damage to the engine pumps, tanks pumps still running (no pressure warnings) and plenty of fuel in the tanks: logically, this points to some restriction between the tank pumps and engine pumps. So far, nothing has been found, so the restriction appears to have been temporary in nature. I presume a lot of time is being spent trying to figure out what this might have been, especially as it affected both L & R systems almost simultaneously.
We're down to contaminant (nothing significant found yet), odd fuel behaviour (ditto), physical change to fuel lines to reduce cross-sectional area (no evidence for this at the moment) and ??
I'm hoping something might come from a detailed environmental test of the fuel supply chain - no news yet...