I deleted a Vmware MD from the webgui and then in the webgui MD page, I clicked the
"Setup New Diskless MD*" button.
Part of that setup re-exports directories for NFS kernel daemon...
Then I started the new vm-md, it announced and then began setting up.
And then I turned on the family room MD - and it worked!
The VM MD finished and works as well.
hope this helps someone - probably I did not actually have to delete the MD.
I suspect that clicking the "Setup New Diskless MD*" button on the MD page in the webgui would have done it.
I have marked this as a "SOLUTION" rather than "SOLVED" because I still do not have a root cause of this unhappiness.