From the report: "In addition, work has commenced on developing a more complete understanding of the dynamics of the fuel as it flows from the fuel tank to the engine."
This may suggest a restriction due to fluidic resonance in a tuned circuit. If the conditions are exactly right and there is some initiating event, a resonance can occur in a pipe that will restrict fluid flow. Given two near identical tuned circuits and operating conditions, the resonance and the resulting fluid restriction will be virtually identical in both circuits. The report mentions near identical engine thrust restriction.
In a structure with two separate systems with near identical geometry and operating conditions, resonance in one system can induce resonance in the other system by mechanical coupling through the structure. Under these conditions, the typical delay between the initial resonance of the first system and the induced resonance of the second system is on the order of 2 to 20 seconds. The report mentions a 7 second delay between the first and the second engine thrust restriction. Note that very little resonant energy needs to be coupled through the structure to induce a resonance in a near identical circuit.
Such a resonance is likely to be at a very low frequency and it should be relatively audible to the ear. However, it is not certain if a resonance of this frequency would be recorded by any of the flight data recorders. Typical audio recorders in aircraft eliminate low frequencies to improve speech intelligibility and the mechanical vibration of the resonance is too small and too fast to be detected as a variation of flight parameters.
I believe that witnesses reported that the aircraft made an unusual sound as it approached the airport. While witnesses tend to be unreliable, some weight might be given to this observation as witnesses who work at airports tend to have experience with typical aircraft noise.
An investigation to include or exclude this possibility would be an extremely difficult and time consuming process.