@ The Shadow.
I think you are reinforcing what I tried to say.
Yes, your analogy to a tumour is good.
I believe that this has been a "latent" problem for some time.
I believe that the key will be found to be low flow rates exacerbated by minimum use of thrust during descent, rather than unique temperature conditions.
Of course low sub zero (normal) fuel temps are a prerequisite.
I still believe that fuel distillation / composition may have a bearing on the issue by impacting the water solubility/temperature characteristics.
So I wonder where flow rates are at their lowest, away from potential energy sources and combined with profile changes that might act as a nucleation site.
I don't believe that the tumour broke away and blocked some downstream area. For this to have occurred at almost the same time in both independent systems is one step too far on the coincidence scale.
We'll have to wait and see.