fragop,
I submitted a support incident for this and was informed it had been elevated to the engineers. It seems there may be two issues. Number one is that when you select a default file, the extension only puts the code in your "update/insert" page some of the time. Number is two is that when the default image is there - it still doesn't make any difference as far as maintaining a default value for the database.
I hope this gets worked out soon.