Extended partitions are not an issue for linux at all… you could have created /home on a samba share on a remote server and bind it to the system without an issue
As you say “lock my workstation” it will be about the used locker command/backend in use.
What ISO do you use for install? As we have had an issue with locker (light-locker) before…
to see this try the keystrokes i give you before (switching to TTY2 and back to TTY7, where TTY7 is where X is running and the Login Manager, TTY2 is one of the virtual Terminals where you can log in textbased to the system)
pacman -Qs light-locker
Also a journal from the timespace where you lock the system would be helpfull:
journalctl --since "10 minutes ago"
will give the journaloutput from last 10 minutes before, you can autopastebin this and provide the link to the log like this:
journalctl --since "10 minutes ago" | curl -F 'f:1=<-' ix.io
it will give you a short url after command is running.