The problem however is identiying the part of the fuel system at fault.
The fuel system apparently did not fail, as such, but rather fuel icing appears to be the cause.
This specific flight was one (perhaps the only one) that did not descend into warmer air along the route, due to very cold ambient temperatures aloft.
Not necessarily the FD crews fault, it could well have been that the actual fuel tank(s) fuel temperatures were incorrectly displayed.