I did watch your video and I run the following on the system istaled as above :Thanks, people …
Whilst reproducibility is ideal, I don't expect everyone to encounter data loss quickly, or in exactly the same way.
For crashes with emulators/virtualbox-ose-additions there's recent analysis at <https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=236917#c6> so (at least for this topic) I think, people should forget about causes of crashes. We can move on from that. As far as I can tell: not a problem with FreeBSD-provided disk images – <https://forums.FreeBSD.org/threads/80655/post-514836> on page one gained a postscript a few days ago (before I realised that bug 254412 was a duplicate), updated this afternoon.
Aeterna if you like, follow the first three minutes of what was recorded there. Fewer steps for you.
The beginning of the recording was the first ever boot of the machine, after growing the disk to 15 GB.
Appearance of the VirtualBox logo at 03:08 on the timeline was a response to me performing a reset of the machine.
sudo pkg install firefox -q -y && sync
nothing happened, firefox is installed. No reboot/reset. All works.
I am not able to reproduce the issue you are reporting.