I am writing this message as openSUSE's maintainer of VirtualBox.
Nearly every update of the Linux kernel to a new 5.X version breaks VirtualBox.
Why do you not know of this fact? It is because I undertake a program of testing
5.X almost immediately after the release of 5.X-1, even before the release of
5.X-rc1. On occasion, the fix is too complicated for someone with a medium
knowledge of the kernel to prepare a fix, and we have to wait for Oracle. This
may be the case here.
In the case of 5.13, the strange thing is that my home-built kernel does not
show the problem, thus I was not aware that this calamity was pending. I am
looking at the differences between my configuration and that of openSUSE to see
if that explains the difference in behavior. Of course, it is possible that
openSUSE makes some patch to their system that causes the breakage. If that is
the case, then neither I nor Oracle will be able to fix it!!
Until this problem is resolved, you have two options:
1. Stay with a 5.12 kernel.
2. Switch to running your VM's using KVM or QEMU. Beware of Vagrant containers.
They have some pitfalls, and you will get no support from me!
Larry