I can reproduce this bug on VirtualBox (Other Linux 64bit) with the x86 ISO -image by rebooting once, starting with 6.37.
6.36.3 and earlier does not have this feature.
So, once installed and booted, '/system reboot', the VM completes reboot, shows a flash of the message "License expired" and shuts down.
I really like to use the 24h full speed trial as demo and lab. "Insane" actually working things like vrrp-terminated eoip-tunnels have been known to be built between VM:s running RouterOS on my laptop