Created attachment 229807 [details]
At least the last 3 releases of 14.0-CURRENT Vagrant boxes have the following panic and failed to boot up:
panic: mutex Giant owned at /usr/src/sys/kern/kern_synch.c:501
Please see the attached screen recording.
The issue appears to be the vboxguest kernel module step. Removing vboxguest_enable="YES" makes the issue disappear.