Seems to be an issue with c-states. 🤖 Could not find much but these sources pointed me in the right direction:
https://bbs.archlinux.org/viewtopic.php?id=263720
https://github.com/opnsense/core/issues/5737
https://en.wikipedia.org/wiki/ACPI#Power_states

Then used...
sysctl hw.acpi.cpu.cx_lowest=C3
...to change the ACPI setting and it seems to work so far. It will consume more energy but I can use my second monitor now at least. 🙃

#acpi #freebsd #cstates