Fuel freezing
At last something I can comment on with authority. Yes, Teal, it can happen but it is incredibly rare. I cant remember the last time I heard of it happening. Moggiee is correct - Jet A (US) has a higher freeze point than Jet A-1 (i.e. it freezes more readily). The current spec for the UK is what used to be called DERD 2494 now renamed DefStan 91-91. The spec is - 47 degrees Celsius. The problem with the freezing /waxing theory is that Chinese jet A-1 equivalent (used to be RP-3, now called jet fuel number 3) typically has a lower freeze point (-52C) than Jet A-1.
Thats not to say it could not have happened or that the particular delivery could not have been waxy. But there will have been retention samples taken and freeze point is a test that will have been carried out by an approved lab. BA do take a keen interest in the fuel that goes into their aircraft and I remember being on the recieving end of an assessment visit in Nairobi with painful clarity. It resulted in us buying a whole bunch of new equipment.
The problem is that the normal freeze point for Kerosene is minus twenty or so. Dual purpose kerosine, which can be used in both aircraft and in domestic appliances has both a low freeze point and a high smoke point.
Mistakes can happen.....
P