Hello @pouicpouic,
When you click on “Update Sort Order”.
Are you able to see the message “Sort order changed”?
Here is a screenshot of that message.
We just made a quick test and we haven’t been able to replicate the problem.
Also, checking those shortcodes. Some of them are a bit older. It will be great if you can re-insert them and check again.
If the problem persists, you probably need to check for conflicts.
– Temporarily deactivate all your plugins except NextGen Gallery.
– Is the problem solved? Then, it was caused by one of your plugins. Please check one by one and find the one causing the problem.
– If the problem is not solved with the deactivation of the plugins, try changing to a standard WordPress theme, it could be a conflict with your current theme.
A full website backup is recommended.
Please keep us posted, we are happy to help!