I have a problem synchronising the iPhone_slider with the tab_slider. It used to work well, but now the first screenshot is not loaded immediately when web site is opened. For about a second it is black and then, once it appears, the screenshot changes to the next one while the tab slider stays on the same place.
The web site is uktheorytest.org.
I am not sure why it stopped working as it used to work extremely well. I was thinking that it might happen because I installed Jetpack, but I have tried turning Photon OFF and it didn’t resolve the issue…