i just had the same thing happen to me 1st time. shutdown the array did a rc.nginx stop, wait it to shutdown the service and API, did a start and at the moment not getting the error anymore for the time being. i did have the red triangle ! on the myserver, I disabled it, went to work and come home and it was reconnected to the API, restarted it and all seemed well and it did a flash basckup.
and yes everything is updated