Fungal growth?
In both tanks at the same growth rate, to cause engines to stop at basically the same time!
Now that would call for some very time consuming road side maintenance on the independent fuel systems.
Such as.
Fuel tank inspection (all wing panels).
All growth removed.
All filters replaced/cleaned.
Again after engine ground runs.
Entire fuel system cleaned.
Possibly even FCU change.
Compulsory placard of some sort and
A bunch of paperwork.
A known quantity of fuel will need to be uploaded after inspections and ground runs, but prior to flight.
Unless this procedure is in the MM the actual maintenance/inspections will be given by CAsA or an Approved Person.
Questions - When the first engine surged why was it shut down?
Why no mention of fuel cross feed and attempted restart first?
Was it the same pilot that flew the aircraft out, as the one that landed it? (Company policy considerations also).
The 441 on one engine is not a slug, so there is time to trouble shoot or follow procedures.
Fuel calibrations are pretty regular and the system from memory pretty accurate and reliable, reweigh of the aircraft also a task to pick up on irregularity (such growth would need to be a fair size and weight), normal filter maintenance would also have signs of contamination.