First, thank you @kiokoman for the link.
When I tried to edit a file, I discovered that pfBlocker caused my /var to fill up.
Since unbound creates a /var/unbound/test and writes tmp files to it, it could not.
Interesting side effect, before it does, it appears that it zero's out the /var/unbound/root.key BEFORE recreating all the necessary files in /var/unbound/test first.
So if /var is full, it appears to break unbound.
I see several issues like:
https://redmine.pfsense.org/issues/8287
https://redmine.pfsense.org/issues/6442
One is not reproducible and the other is labeled not a bug.
Fill up /var as a test to reproduce.
I would think on memory constrained devices (like Arm based pfSense hardware) you would want to check free space before writing temp/test files but maybe that's not considered a bug.... but removing the root.key (the file ends up zero length) and not being able to restart unbound after freeing up space in /var seems like a bug to me... ?