Hello Micheal
The problem arises when there are a lot of photo files to download and the host’s server is loaded, the file download process falls into a MySQL time-out when the archive file is created.
The solution on a dedicated server would be to modify the Mysql settings.
But on a shared server like ours, like many Joomla users, it’s impossible to change the Mysql settings.
The recommended solution, then, is to add regular exchanges with the database using mysql_ping() to avoid time-out.
Thanks for finding a solution