Hi Cais,
I’ve tried to rollback before I update everything. It seems that the issue appears after I’ve updated the WPML plugins.
WPML Multilingual CMS from 3.1.9.7 to 3.2.7
WPML String Translation from 2.1.4 to 2.2.6
Now, the problem is how I could retain the previous behavior of nextgen gallery even though I updated WPML?