I see.
Nested virtualization is rather unpopular and not tested by any Whonix developers as far as I am aware. More so when mixing virtualizers (VMware + VirtualBox). You might be literally the only person in this universe doing this. I recommend to stick to more common setups of Whonix.
Also Self Support First Policy for Whonix might apply - would Debian XFCE in a VirtualBox VM run which itself runs nested in VMware? This might very well cause similar issues.