Answering my own questions this worked for me
sudo su
csrutil clear
reboot
Then uninstall (from the official uninstaller) and re-install virtualbox. If needed go to System Preferences - Privacy - General and accept the extensions. Reboot again.
as suggested in https://forums.virtualbox.org/viewtopic.php?f=39&t=98763&sid=7541dfcace7a86fdb5bc8a281296ad94&start=75#p488555
