Continuing on, in this incident, it appears that an inadvertent "bump" of the runway dropdown may have caused the problem. It is much less likely that the error would have been replicated had the FO done the planning on his laptop as well ie he would have had to bump the same dropdown, despite the bug in the software. The error would then have manifested itself in the figures comparison. Perhaps Airbus was worried enough about the robustness of the "concept" (read software/human failings?) that it suggested "independent" calculations, something that Easyjet elected not to do. To me, "independent" is either on separate machines then compared, or the same machine with all input values wiped and done again to compare with the first run.