Hi Enrico,
yes, see a previous discussion. Specifically, considering the scoring resolution you ask for, you need a FLUKAFIX card limiting the fraction of kinetic energy lost in a step down to 0.02 or less (instead of the default PRECISIO value of 0.05). With
FLUKAFIX 0.02 LiF
I get:
(which may suggest to even lower to 0.01).