All the Execute SQL Task does is execute your script - so, if that script is not completing all of the tasks then the script has to be the problem.

This could be related to how you are looping through the databases. You could be running into an issue where you are trying to access the hidden database snapshot and trying to back it up - which would cause your script to fail.

You could be trying to access an offline database - which could cause your script to fail. Or, something else...

If your script is not written to return an error, it would appear to complete successfully 'after 7 minutes' but not actually complete the tasks.