I purchased the AZ about a month ago, I'am having the same issue.
Mine only does it when I do a delete all channels first and then scan.
If I do a blind scan without deleting channels first it doesn't happen.
Hope this helps.
When you say you are deleting all channels, do you mean all channels across all satellites using the "Delete all channels" from the Installation menu or using the "Delete current satellite channels" menu option from the satellite list? With the current firmware versions, I do believe that there has to be at least 1 channel on the satellite you are blind scanning so you should never be using the "Delete all channels" option before doing a blind scan as this deletes all channels across all satellites.
Using the "Delete current satellite channels" menu option deletes all channels from the current satellite except the currently tuned one so this would be the option to use in order to quickly remove inactive channels for a specific satellite before doing a blind scan.