Coub video slows down when you turn on the sound! How to fix?

Question

Android

When I turn on the video with Coub, it works fine, but when I click again on the video to turn on the sound, the picture starts to lag and I get a slide show. There is no such thing on YouTube and in the VK player. My phone is Lenovo a680 android 4.2.2 (I tried a lot of browsers). Please help!