Launcher doesn't correctly switch between user accounts stored in the profiles

I have three versions currently created (one for me, one for my brother, and the default one). The problem is that it only seems to load the account stored in the first profile. If I hack the system using the JSONs to start with my brother's profile, it works fine (except for the password). However, if I switch to another profile which has the same log in as the LASTLOGIN file on disc, it "locks" onto that log in and won't automatically change back to my brother's credentials without a restart.