As both users seem to have the same rights and it's just one pernr skipped, a quicj guess would be: it's skipping the pernr assigned to the user (IT0105, subty 0001), because auth object p_pernr is blocking it. Maybe the second user doesn't have an assignment in IT0105.
But transaction SU53 or a trace via ST01 should give you more information to approach the problem, if this quicj guess is not the solution.