"automatically assigned by the software" isn't the case; generally this means that you've left a configuration file in /etc/modprobe.d with the option active.
grep -n 6stack /etc/modprobe.d/*
"automatically assigned by the software" isn't the case; generally this means that you've left a configuration file in /etc/modprobe.d with the option active.
grep -n 6stack /etc/modprobe.d/*