Hi @tclonglpc and @photocrati
Running WP 4.7.2 over here and I had a similar problem as @tclonglpc with the plugin not playing well with NextGEN Gallery 2.1.77. I also observed that disabling NextGEN fixed the slideshow with no other action required and re-enabling it reintroduces the problem. So this is not a single site issue. The issue first came up in October 2016 for me. Used another plugin before finding this post.
I also tested duplicating an existing gallery back then but it did not fix the problem.
Hope this helps
Happy user
